Temperature effect on shear behavior of ore-backfill ...
Transcript of Temperature effect on shear behavior of ore-backfill ...
Temperature effect on shear behavior of ore-backfill couplingspecimens at various shear directions
JIANG Fei-fei(江飞飞)1 2 ZHOU Hui(周辉)1 2 SHENG Jia(盛佳)3 4
LI Xiang-dong(李向东)3 KOU Yong-yuan(寇永渊)5
1 State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock andSoil Mechanics Chinese Academy of Sciences Wuhan 430071 China2 University of Chinese Academy of Sciences Beijing 100049 China
3 National Engineering Research Center for Metal Mining Changsha Institute of Mining Research Co LtdChangsha 410012 China
4 School of Resource amp Environment and Safety Engineering Hunan University of Science and TechnologyXiangtan 411201 China
5 Jinchuan Group Co Ltd Jinchang 737104 China
copy Central South University Press and Springer-Verlag GmbH Germany part of Springer Nature 2021
Abstract Understanding the temperature effect on shear behavior of the ore-backfill coupling structure is critical for thesafety and stability of backfill stope under the condition of high horizontal stress in deep mining Direct shear tests werecarried out on the cemented rod-mill sand backfill (CRB) and ore-CRB (OCRB) coupling specimens at varioustemperatures (20 40 and 60 degC) The shear behavior and AE characteristic parameters of OCRB at different sheardirections were compared and analyzed The results show that the temperature effect on the shear performance of CRBmainly depends on the characteristics of microstructures and main mineral phases the performance of CRB at 40 degC isrelatively good the shear deformation of OCRB has one more ldquopeak fluctuation stagerdquo than CRB and has a goodcorrelation with AE characteristic parameters The temperature can positively or negatively impact the shear strength ofOCRB depending on the temperature and shear direction the shear performance of OCRB along the axis direction (D1)is significantly better than that perpendicular to the axis direction (D2) The co-bearing capacity of the ore-backfillcoupling structure (ie stopes) is closely related to the ambient temperature and principal stress orientation
Key words cemented backfill ore-backfill temperature shear direction shear strength AE energy
Cite this article as JIANG Fei-fei ZHOU Hui SHENG Jia LI Xiang-dong KOU Yong-yuan Temperature effect onshear behavior of ore-backfill coupling specimens at various shear directions [J] Journal of Central South University2021 28(10) 3173minus3189 DOI httpsdoiorg101007s11771-021-4841-4
1 Introduction
The backfill mining method has been widely
applied in underground mines due to its advantagesin surface subsidence control mined-out voidstreatment high recovery ratio solid waste disposaland environmental protection [1minus 3] Cemented
DOI httpsdoiorg101007s11771-021-4841-4
Foundation item Project(KFJ-STS-QYZD-174) supported by the Science and Technology Service Network Initiative of the ChineseAcademy of Sciences Projects(41941018 42077251) supported by the National Natural Science Foundation of ChinaProject(P2018G045) supported by the Science amp Technology Research and Development Program of China RailwayProject(2018CFA013) supported by the Hubei Provincial Natural Science Foundation Innovation Group China
Received date 2020-04-17 Accepted date 2021-01-12Corresponding author JIANG Fei-fei PhD Research Assistant Tel +86-17607189836 E-mail ffjiangwhrsmaccn ORCID https
orcidorg0000-0002-3453-2510
J Cent South Univ (2021) 28 3173-3189
J Cent South Univ (2021) 28 3173-3189
backfill is a homogeneous mixture of aggregatebinder and water and its physico-mechanicalproperties have always been one of the criticalresearch contents of many scholars [4minus7]
For the deep backfill mines under the conditionof high horizontal stress the backfill andsurrounding rock will bond to form a couplingco-bearing structure after the filling slurry istransported to the stopes The ambient temperatureand principal stress orientation of deep mining oftendirectly affect the physico-mechanical properties ofbackfill and rock-backfill coupling structure thus toaffect the safety and stability of backfill stopes Atpresent many studies have been carried out toinvestigate the influence of temperature onmechanical properties of backfill and somevaluable results have been obtained Previousstudies have revealed that the temperature cansignificantly affect the process and rate of cementhydration of backfill as well as the pore structuresinside the backfill thus affecting the strengthdevelopment of backfill [8 minus 10] ALDHAFEERIet al [11] confirmed that the reactivity of cementedpaste backfill (CPB) is temperature-dependent bylaboratory tests and the numerical model proposedby NASIR et al [12] also proved that the strengthdevelopment of CPB is closely related to thetemperature and the degree of hydration Laboratorytests have been performed by FALL et al [13 14] toexplore the mechanical properties of cementedtailings backfill (CTB) at various temperatures WUet al [15] simulated the influence of temperature onthe hydraulic behavior of CTB based on COMSOLmultiphysics Although the temperature has asignificant influence on the mechanical performanceof backfill the existing researches have proved thatthe effect of temperature on the mechanicalbehaviors of rock can be ignored within acertain range of temperature (generally below 100 degC)[16 17] Due to the different sensitivity of rock andbackfill to temperature the mechanical behaviors ofrock and backfill are different at varioustemperatures thus affecting the overall mechanicalresponse of rock-backfill coupling structureTherefore it is of great significance to conductrelevant experimental studies for understanding themechanical properties of rock-backfill couplingstructure under the deep high-temperature
environmentThis experimental study takes the deep backfill
mining of Jinchuan No 2 mine as the researchbackground and the current mining depth hasreached more than 800 m [18 19] With the increaseof mining depth the mine is facing the unfavorableconditions of continuously increasing temperatureand high horizontal stress According to thestatistics the average geothermal gradient of themining area is 284 deg C100 m which is located inthe Hexi Corridor of Gansu province in NorthwestChina [20] It can be predicted that the deep rockand backfill in the mine will be inevitably exposedto the ambient temperatures of 20minus60 degC in the nextfew decades Furthermore the maximum principalstress is the horizontal tectonic stress which is closeto 50 MPa at the levels of 1000 and 850 and theratio of the horizontal stress to vertical stress can beup to 2 The interval stoping technology is adoptedand the backfill of the primary stope and theorebody of the secondary stope are interlaced Theaxial direction of designed backfill stopes is mostlyparallel or perpendicular to the orientation ofmaximum horizontal principal stress due to the needfor stoping cycles Therefore high horizontal stresswill exert transverse shear stress on the backfillstope and it is necessary to conduct shear tests atvarious temperatures and shear directions Howeverthere is a lack of understanding the temperatureeffect on the shear behavior of the rock-backfillcoupling structure in the deep backfill miningconditions and the relevant research findings arescarce as far as we know Besides there is no reporton the influence of shear direction on the shearbehavior of the rock-backfill coupling structure
In this paper direct shear tests were carried outon the cemented rod-mill sand backfill (CRB) andore-CRB (OCRB) coupling specimens at varioustemperatures (20 40 and 60 ordmC) A PAC-DISPsystem was used to record the acoustic emission(AE) signals during the whole shearing processBased on the shear test results of CRB at varioustemperatures the temperature effect on the shearbehavior and AE characteristic parameters of OCRBat three different shear directions were comparedand analyzed Two aspects of novelty arehighlighted in this paper 1) The revelation of thetemperature effect on shear behaviors of backfill
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and ore-backfill coupling structure under highhorizontal stress and 2) The exploration of theinfluence of shear direction on the shearperformance of ore-backfill coupling structure Thefindings presented in this paper provide some basisfor safety evaluation and design of deep backfillstopes
2 Experimental set-up
21 MaterialsThe rod-mill sand (RMS) was used in this
study derived from the sand silo of the backfillplant on the surface in Jinchuan No 2 mineAccording to the main physicochemical propertiesof test results as shown in Tables 1 2 and Figure 1the coefficient of uniformity and coefficient ofcurvature of RMS are 17226 and 1184respectively indicating that the RMS is well-gradedThe RMS contains high silica content (exceed 70)and low sulfur content which is conducive toimproving the strength of cemented backfill[21 22] The Jinchang Portland cement (JPC)produced by a local cement plant in Jinchang was
used as the hydraulic binder in the experimentalinvestigations The JPC and RMS were blended in aratio of 2080 Tap water in the laboratory was usedto mix the solid mass (total mass of dry RMS andJPC) the pH value of mixing water was 763 andthe mass ratio of water to total solid was 2278
22 Specimen preparationTwo types of cube specimens CRB and OCRB
coupling specimens with a side length of 50 mmwere involved in the experimental study Figure 2shows the specimen preparation procedures indetail 1) The ore was taken from the 1000 m levelof Jinchuan No 2 mine and the average uniaxialcompressive strength (UCS) of intact ore sampleswas 129 MPa The intact ore specimens withdimensions of 50 mmtimes50 mmtimes50 mm wereobtained by using the techniques of cutting andpolishing Then to minimize the processing damageto the ore specimens a computer numerical control(CNC) router was used to carve the square hole (25mmtimes 25 mmtimes50 mm) in the middle of intact orespecimens 2) In the preparation of backfill slurryput the required amount of dry RMS and JPC into amixing container and the solid mass was well-mixed after being stirred for 5 min Then therequired amount of water was added to the containerand stirred for another 10 min until the slurry wasmixed homogeneously Next the slurry can bepoured into the cube dismountable transparentacrylic molds and the hollow section of orespecimens The molds can be removed after waitingfor 12 h for the initial setting at room temperature(20 degC) and then the CRB and OCRB specimenswere cured in a programmable constant temperatureand humidity curing box
A total of 45 specimens including 36 CRB
Table 1 Physical properties of RMS
Parameter
Particle density(g∙cmminus3)
Porosity
D10mm
D30mm
D50mm
D60mm
D90mm
Cu
Cc
RMS
267
4064
0124
0560
1434
2136
2771
17226
1184
Note Di is the particle size at i passing Cu is the coefficient ofuniformity Cu=D60D10 Cc is the coefficient of curvature Cc=D2
30(D10timesD60)
Table 2 Main chemical compositions of RMS and JPC(wt)
Sample
RMS
JPC
SiO2
7147
25
Al2O3
105
758
CaO
441
4992
Na2O
344
057
Sample
RMS
JPC
K2O
297
098
Fe2O3
28
314
MgO
202
234
SO3
113
457
Figure 1 Particle size sieving results of RMS
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J Cent South Univ (2021) 28 3173-3189
specimens and 9 OCRB specimens were prepared
using the procedures mentioned above Thereinto
the CRB specimens were continuously cured for
28 d in a constant temperature (20plusmn05) degC and
constant humidity of (95plusmn1) while the OCRB
specimens were continuously cured for 28 d in a
constant humidity of (95plusmn1) at varioustemperatures (20 40 and 60 deg C) After the curingprocess was completed the laboratory tests can beperformed according to the testing program
23 Testing programThe testing program is shown in Table 3 The
CRB specimens were tested at four various normalstresses (200 300 400 and 500 kPa) while theOCRB specimens were tested at three differentshear directions (D1 along the axis D2perpendicular to the axis D3 perpendicular to theaxial plane) The shear planes of OCRB at differentshear directions consist of ore and backfill (i eCRB) in which D1 and D2 have the same shearplane area (i e the backfill and ore accounted for50 each) while the backfill and ore account for25 and 75 of the shear plane area at D3respectively as shown in Figure 3
24 Testing methodsA RJST-616 shear tester (Developed by
Institute of Rock and Soil Mechanics ChineseAcademy of Sciences China) was employed tostudy the shear behavior of CRB and OCRBspecimens In the shear test the force-control modewas first used to load the normal force to a specifiedvalue and keep it constant Then the displacement-control mode was adopted to load the shear force ata rate of 03 mmmin and the test was stoppedautomatically when the shear displacement reached8 mm During the shear tests a PAC-DISP systemwas adopted to collect the AE signals and at leastone Nano-30 miniature AE sensor was mounted atthe surface of the lower part of the tested specimens(as shown in Figure 4(d)) The coupling agent wasapplied between the sensor and the specimen the
Figure 2 Specimen preparation procedures of CRB andOCRB specimensin detail
Table 3 Laboratory testing program of CRB and OCRB specimens under different conditions
Specimen type
CRB
OCRB
Age timed
28
28
28
28
28
28
TemperaturedegC
20
40
60
20
40
60
Normal stresskPa
200 300 400 500
200 300 400 500
200 300 400 500
500
500
500
Shear direction
mdash
mdash
mdash
D1D2D3
Parameter
PSSRSS
AE Signal
PSSAE Signal
Note All specimens were cured at constant humility of (95plusmn1) D1 is the direction along the axis D2 is the direction perpendicular to theaxis D3 is the direction perpendicular to the axial plane
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pre-amplification was set to 40 dB and the AE
detection threshold was fixed at 45 dB and the
acquisition rate of AE signals was set to 1 MSPS
The direct shear tester and AE acquisition system
are shown in Figure 4
As a common non-destructive testing (NDT)
technology in the field of geotechnical engineering
the AE technology can be used to analyze the
cracking process of rock [23minus26] Cracking process
analysis based on AE technology involves a variety
of related characteristic parameters such as hit
event rate count frequency and energy among
which the hitevent rate and AE energy rate are
often considered as the critical parameters in
the shear failure process analysis [27minus29] The AE
energy released during the shear failure process can
Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3
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be calculated with the following equations [30 31]
Ei =1R intti
tj
U 2 ( t )dt (1)
E =sumEi (2)
where R is the input impedance of voltage
measurement ti and tj are the beginning and ending
time of AE event segment respectively Ei is the
absolute energy obtained by the AE probe during
the time of tj minus ti U(t) is the voltage value of AE
event related to the time t E is the total absolute
energy during the whole shearing process
3 Experimental results and analysis
31 Temperature effect on shear mechanical and
microstructure properties of CRB
311 Shear cracking processes
Figure 5 shows the relationship between shear
stress and shear displacement of CRB at various
temperatures The results indicate that the shear
deformation behaviors at different temperatures are
consistent and in general they can be divided into
four stages initial compaction stage (I) pre-peak
elastic deformation stage (II) post-peak plastic
deformation stage (III) residual deformation
stage (IV) In stage I the shear stress increases
slowly with the shear displacement due to the
contact gap between specimen and shear box and
voids inside the CRB In stage II the shear stress
increases rapidly and linearly with the shear
displacement until it reaches the peak shear strength
(PSS) and in general the PSS can be achieved
within the range of 1minus3 mm shear displacement The
shear stress decreases gently with the shear
displacement in stage III and tends to be stable after
Figure 4 Direct shear tester and AE acquisition system
Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures
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entering stage IV With the increase of temperature
(e g from 20 to 40 ordmC) the PSS and peak shear
displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]
To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the
residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage
Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The
Figure 6 AE hit response during shear test of CRB at20 degC
Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC
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higher the temperature the more concentrated theenergy release For example the interval length of
shear displacement of AE energy released at 20 ordmC
is 54 mm while those at 40 and 60 ordmC are 35 and
23 mm respectively After entering the stable
period the cumulative AE energy of 20 40 and
60 ordmC are 1592times106 857times106 and 2218times106 aJ
respectively indicating that the energy release of
CRB during the shear failure process at 40 ordmC is
gentle while that at 60 ordmC is stronger
312 Shear strength parameters
Figure 8 shows the test results of shear strength
parameters of CRB at various temperatures
indicating that the temperature has a significant
influence on both peak shear strength (PSS) and
residual shear strength (RSS) of CRB The
temperature can have a positive effect on the PSS
while it may have a negative impact on RSS For
example the RSS at 40 and 60 ordmC is lower than that
at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8
under the same conditions Besides the shear
strength and normal stress at various temperatures
are in a good linear relationship and the correlation
coefficient R2 of linear fitting is all greater than
092 Therefore it can be considered that the shear
failure of CRB at various temperatures meets
the Mohr-Coulomb criterion [34minus36] and strength
criterion formulas are as follows
τp = cp + σn tanϕp (3)
τr = cr + σn tanϕr (4)
where τp and τr are peak shear strength and residual
shear strength respectively cp and cr are peak
cohesion and residual cohesion respectively ϕp and
ϕr are peak angle of internal friction and residual
angle of internal friction respectively σn is the
normal stress
Table 4 shows the calculation results of the
peak shear strength and shear strength parameters at
various temperatures according to Eqs (3) and (4)
The peak cohesion cp ranges from 145012 to
155821 kPa and it is positively correlated with the
temperature The peak angle of internal friction ϕp is
between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)
The residual cohesion cr ranges from 8053 to
4048 kPa and the maximum cr value is at 40 ordmC
The residual angle of internal friction ϕr is between
Table 4 Linear fitting results of shear strength parameters of CRB
Group
I
II
III
TemperaturedegC
20
40
60
Peak strength parameter
Fitting formula
y1= 145012+115x1
y2= 154614+105x2
y3= 155821+116x3
Correlationcoefficient
R2
0923
0952
0990
CohesioncpkPa
145012
154614
155821
Internalfrictionangleϕp(deg)
4899
4640
4924
Residual strength parameter
Fitting formula
y1=4602+102x1
y2=8053+075x2
y3=4048+096x3
Correlationcoefficient
R2
0999
0978
0975
CohesioncrkPa
4602
8053
4048
Internalfrictionangleϕr(deg)
4557
3687
4383
Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS
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3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
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divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
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trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
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entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
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J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
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J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
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[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
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[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
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[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
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[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
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[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
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LI Xiang-dong Effects of temperature and age on physico-
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[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
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Underground Space Technology 2020 99 103379 DOI
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[34] BAREITHER C A BENSON C H EDIL T B Comparison
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[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
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[36] LI Li Generalized solution for mining backfill design [J]
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04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
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[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
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Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
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[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
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[41] LI Wen-chen FALL M Sulphate effect on the early age
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[42] SHANG J ZHAO Z MA S On the shear failure of incipient
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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
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(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
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J Cent South Univ (2021) 28 3173-3189
backfill is a homogeneous mixture of aggregatebinder and water and its physico-mechanicalproperties have always been one of the criticalresearch contents of many scholars [4minus7]
For the deep backfill mines under the conditionof high horizontal stress the backfill andsurrounding rock will bond to form a couplingco-bearing structure after the filling slurry istransported to the stopes The ambient temperatureand principal stress orientation of deep mining oftendirectly affect the physico-mechanical properties ofbackfill and rock-backfill coupling structure thus toaffect the safety and stability of backfill stopes Atpresent many studies have been carried out toinvestigate the influence of temperature onmechanical properties of backfill and somevaluable results have been obtained Previousstudies have revealed that the temperature cansignificantly affect the process and rate of cementhydration of backfill as well as the pore structuresinside the backfill thus affecting the strengthdevelopment of backfill [8 minus 10] ALDHAFEERIet al [11] confirmed that the reactivity of cementedpaste backfill (CPB) is temperature-dependent bylaboratory tests and the numerical model proposedby NASIR et al [12] also proved that the strengthdevelopment of CPB is closely related to thetemperature and the degree of hydration Laboratorytests have been performed by FALL et al [13 14] toexplore the mechanical properties of cementedtailings backfill (CTB) at various temperatures WUet al [15] simulated the influence of temperature onthe hydraulic behavior of CTB based on COMSOLmultiphysics Although the temperature has asignificant influence on the mechanical performanceof backfill the existing researches have proved thatthe effect of temperature on the mechanicalbehaviors of rock can be ignored within acertain range of temperature (generally below 100 degC)[16 17] Due to the different sensitivity of rock andbackfill to temperature the mechanical behaviors ofrock and backfill are different at varioustemperatures thus affecting the overall mechanicalresponse of rock-backfill coupling structureTherefore it is of great significance to conductrelevant experimental studies for understanding themechanical properties of rock-backfill couplingstructure under the deep high-temperature
environmentThis experimental study takes the deep backfill
mining of Jinchuan No 2 mine as the researchbackground and the current mining depth hasreached more than 800 m [18 19] With the increaseof mining depth the mine is facing the unfavorableconditions of continuously increasing temperatureand high horizontal stress According to thestatistics the average geothermal gradient of themining area is 284 deg C100 m which is located inthe Hexi Corridor of Gansu province in NorthwestChina [20] It can be predicted that the deep rockand backfill in the mine will be inevitably exposedto the ambient temperatures of 20minus60 degC in the nextfew decades Furthermore the maximum principalstress is the horizontal tectonic stress which is closeto 50 MPa at the levels of 1000 and 850 and theratio of the horizontal stress to vertical stress can beup to 2 The interval stoping technology is adoptedand the backfill of the primary stope and theorebody of the secondary stope are interlaced Theaxial direction of designed backfill stopes is mostlyparallel or perpendicular to the orientation ofmaximum horizontal principal stress due to the needfor stoping cycles Therefore high horizontal stresswill exert transverse shear stress on the backfillstope and it is necessary to conduct shear tests atvarious temperatures and shear directions Howeverthere is a lack of understanding the temperatureeffect on the shear behavior of the rock-backfillcoupling structure in the deep backfill miningconditions and the relevant research findings arescarce as far as we know Besides there is no reporton the influence of shear direction on the shearbehavior of the rock-backfill coupling structure
In this paper direct shear tests were carried outon the cemented rod-mill sand backfill (CRB) andore-CRB (OCRB) coupling specimens at varioustemperatures (20 40 and 60 ordmC) A PAC-DISPsystem was used to record the acoustic emission(AE) signals during the whole shearing processBased on the shear test results of CRB at varioustemperatures the temperature effect on the shearbehavior and AE characteristic parameters of OCRBat three different shear directions were comparedand analyzed Two aspects of novelty arehighlighted in this paper 1) The revelation of thetemperature effect on shear behaviors of backfill
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and ore-backfill coupling structure under highhorizontal stress and 2) The exploration of theinfluence of shear direction on the shearperformance of ore-backfill coupling structure Thefindings presented in this paper provide some basisfor safety evaluation and design of deep backfillstopes
2 Experimental set-up
21 MaterialsThe rod-mill sand (RMS) was used in this
study derived from the sand silo of the backfillplant on the surface in Jinchuan No 2 mineAccording to the main physicochemical propertiesof test results as shown in Tables 1 2 and Figure 1the coefficient of uniformity and coefficient ofcurvature of RMS are 17226 and 1184respectively indicating that the RMS is well-gradedThe RMS contains high silica content (exceed 70)and low sulfur content which is conducive toimproving the strength of cemented backfill[21 22] The Jinchang Portland cement (JPC)produced by a local cement plant in Jinchang was
used as the hydraulic binder in the experimentalinvestigations The JPC and RMS were blended in aratio of 2080 Tap water in the laboratory was usedto mix the solid mass (total mass of dry RMS andJPC) the pH value of mixing water was 763 andthe mass ratio of water to total solid was 2278
22 Specimen preparationTwo types of cube specimens CRB and OCRB
coupling specimens with a side length of 50 mmwere involved in the experimental study Figure 2shows the specimen preparation procedures indetail 1) The ore was taken from the 1000 m levelof Jinchuan No 2 mine and the average uniaxialcompressive strength (UCS) of intact ore sampleswas 129 MPa The intact ore specimens withdimensions of 50 mmtimes50 mmtimes50 mm wereobtained by using the techniques of cutting andpolishing Then to minimize the processing damageto the ore specimens a computer numerical control(CNC) router was used to carve the square hole (25mmtimes 25 mmtimes50 mm) in the middle of intact orespecimens 2) In the preparation of backfill slurryput the required amount of dry RMS and JPC into amixing container and the solid mass was well-mixed after being stirred for 5 min Then therequired amount of water was added to the containerand stirred for another 10 min until the slurry wasmixed homogeneously Next the slurry can bepoured into the cube dismountable transparentacrylic molds and the hollow section of orespecimens The molds can be removed after waitingfor 12 h for the initial setting at room temperature(20 degC) and then the CRB and OCRB specimenswere cured in a programmable constant temperatureand humidity curing box
A total of 45 specimens including 36 CRB
Table 1 Physical properties of RMS
Parameter
Particle density(g∙cmminus3)
Porosity
D10mm
D30mm
D50mm
D60mm
D90mm
Cu
Cc
RMS
267
4064
0124
0560
1434
2136
2771
17226
1184
Note Di is the particle size at i passing Cu is the coefficient ofuniformity Cu=D60D10 Cc is the coefficient of curvature Cc=D2
30(D10timesD60)
Table 2 Main chemical compositions of RMS and JPC(wt)
Sample
RMS
JPC
SiO2
7147
25
Al2O3
105
758
CaO
441
4992
Na2O
344
057
Sample
RMS
JPC
K2O
297
098
Fe2O3
28
314
MgO
202
234
SO3
113
457
Figure 1 Particle size sieving results of RMS
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J Cent South Univ (2021) 28 3173-3189
specimens and 9 OCRB specimens were prepared
using the procedures mentioned above Thereinto
the CRB specimens were continuously cured for
28 d in a constant temperature (20plusmn05) degC and
constant humidity of (95plusmn1) while the OCRB
specimens were continuously cured for 28 d in a
constant humidity of (95plusmn1) at varioustemperatures (20 40 and 60 deg C) After the curingprocess was completed the laboratory tests can beperformed according to the testing program
23 Testing programThe testing program is shown in Table 3 The
CRB specimens were tested at four various normalstresses (200 300 400 and 500 kPa) while theOCRB specimens were tested at three differentshear directions (D1 along the axis D2perpendicular to the axis D3 perpendicular to theaxial plane) The shear planes of OCRB at differentshear directions consist of ore and backfill (i eCRB) in which D1 and D2 have the same shearplane area (i e the backfill and ore accounted for50 each) while the backfill and ore account for25 and 75 of the shear plane area at D3respectively as shown in Figure 3
24 Testing methodsA RJST-616 shear tester (Developed by
Institute of Rock and Soil Mechanics ChineseAcademy of Sciences China) was employed tostudy the shear behavior of CRB and OCRBspecimens In the shear test the force-control modewas first used to load the normal force to a specifiedvalue and keep it constant Then the displacement-control mode was adopted to load the shear force ata rate of 03 mmmin and the test was stoppedautomatically when the shear displacement reached8 mm During the shear tests a PAC-DISP systemwas adopted to collect the AE signals and at leastone Nano-30 miniature AE sensor was mounted atthe surface of the lower part of the tested specimens(as shown in Figure 4(d)) The coupling agent wasapplied between the sensor and the specimen the
Figure 2 Specimen preparation procedures of CRB andOCRB specimensin detail
Table 3 Laboratory testing program of CRB and OCRB specimens under different conditions
Specimen type
CRB
OCRB
Age timed
28
28
28
28
28
28
TemperaturedegC
20
40
60
20
40
60
Normal stresskPa
200 300 400 500
200 300 400 500
200 300 400 500
500
500
500
Shear direction
mdash
mdash
mdash
D1D2D3
Parameter
PSSRSS
AE Signal
PSSAE Signal
Note All specimens were cured at constant humility of (95plusmn1) D1 is the direction along the axis D2 is the direction perpendicular to theaxis D3 is the direction perpendicular to the axial plane
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J Cent South Univ (2021) 28 3173-3189
pre-amplification was set to 40 dB and the AE
detection threshold was fixed at 45 dB and the
acquisition rate of AE signals was set to 1 MSPS
The direct shear tester and AE acquisition system
are shown in Figure 4
As a common non-destructive testing (NDT)
technology in the field of geotechnical engineering
the AE technology can be used to analyze the
cracking process of rock [23minus26] Cracking process
analysis based on AE technology involves a variety
of related characteristic parameters such as hit
event rate count frequency and energy among
which the hitevent rate and AE energy rate are
often considered as the critical parameters in
the shear failure process analysis [27minus29] The AE
energy released during the shear failure process can
Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3
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J Cent South Univ (2021) 28 3173-3189
be calculated with the following equations [30 31]
Ei =1R intti
tj
U 2 ( t )dt (1)
E =sumEi (2)
where R is the input impedance of voltage
measurement ti and tj are the beginning and ending
time of AE event segment respectively Ei is the
absolute energy obtained by the AE probe during
the time of tj minus ti U(t) is the voltage value of AE
event related to the time t E is the total absolute
energy during the whole shearing process
3 Experimental results and analysis
31 Temperature effect on shear mechanical and
microstructure properties of CRB
311 Shear cracking processes
Figure 5 shows the relationship between shear
stress and shear displacement of CRB at various
temperatures The results indicate that the shear
deformation behaviors at different temperatures are
consistent and in general they can be divided into
four stages initial compaction stage (I) pre-peak
elastic deformation stage (II) post-peak plastic
deformation stage (III) residual deformation
stage (IV) In stage I the shear stress increases
slowly with the shear displacement due to the
contact gap between specimen and shear box and
voids inside the CRB In stage II the shear stress
increases rapidly and linearly with the shear
displacement until it reaches the peak shear strength
(PSS) and in general the PSS can be achieved
within the range of 1minus3 mm shear displacement The
shear stress decreases gently with the shear
displacement in stage III and tends to be stable after
Figure 4 Direct shear tester and AE acquisition system
Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures
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J Cent South Univ (2021) 28 3173-3189
entering stage IV With the increase of temperature
(e g from 20 to 40 ordmC) the PSS and peak shear
displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]
To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the
residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage
Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The
Figure 6 AE hit response during shear test of CRB at20 degC
Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC
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J Cent South Univ (2021) 28 3173-3189
higher the temperature the more concentrated theenergy release For example the interval length of
shear displacement of AE energy released at 20 ordmC
is 54 mm while those at 40 and 60 ordmC are 35 and
23 mm respectively After entering the stable
period the cumulative AE energy of 20 40 and
60 ordmC are 1592times106 857times106 and 2218times106 aJ
respectively indicating that the energy release of
CRB during the shear failure process at 40 ordmC is
gentle while that at 60 ordmC is stronger
312 Shear strength parameters
Figure 8 shows the test results of shear strength
parameters of CRB at various temperatures
indicating that the temperature has a significant
influence on both peak shear strength (PSS) and
residual shear strength (RSS) of CRB The
temperature can have a positive effect on the PSS
while it may have a negative impact on RSS For
example the RSS at 40 and 60 ordmC is lower than that
at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8
under the same conditions Besides the shear
strength and normal stress at various temperatures
are in a good linear relationship and the correlation
coefficient R2 of linear fitting is all greater than
092 Therefore it can be considered that the shear
failure of CRB at various temperatures meets
the Mohr-Coulomb criterion [34minus36] and strength
criterion formulas are as follows
τp = cp + σn tanϕp (3)
τr = cr + σn tanϕr (4)
where τp and τr are peak shear strength and residual
shear strength respectively cp and cr are peak
cohesion and residual cohesion respectively ϕp and
ϕr are peak angle of internal friction and residual
angle of internal friction respectively σn is the
normal stress
Table 4 shows the calculation results of the
peak shear strength and shear strength parameters at
various temperatures according to Eqs (3) and (4)
The peak cohesion cp ranges from 145012 to
155821 kPa and it is positively correlated with the
temperature The peak angle of internal friction ϕp is
between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)
The residual cohesion cr ranges from 8053 to
4048 kPa and the maximum cr value is at 40 ordmC
The residual angle of internal friction ϕr is between
Table 4 Linear fitting results of shear strength parameters of CRB
Group
I
II
III
TemperaturedegC
20
40
60
Peak strength parameter
Fitting formula
y1= 145012+115x1
y2= 154614+105x2
y3= 155821+116x3
Correlationcoefficient
R2
0923
0952
0990
CohesioncpkPa
145012
154614
155821
Internalfrictionangleϕp(deg)
4899
4640
4924
Residual strength parameter
Fitting formula
y1=4602+102x1
y2=8053+075x2
y3=4048+096x3
Correlationcoefficient
R2
0999
0978
0975
CohesioncrkPa
4602
8053
4048
Internalfrictionangleϕr(deg)
4557
3687
4383
Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS
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J Cent South Univ (2021) 28 3173-3189
3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
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J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
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J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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397minus413 DOI 101016jenggeo201005016
[14] FALL M POKHAREL M Coupled effects of sulphate and
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1016jcemconcomp201008002
[15] WU Di CAI Si-jing Coupled effect of cement hydration and
temperature on hydraulic behavior of cemented tailings
backfill [J] Journal of Central South University 2015 22(5)
1956minus1964 DOI 101007s11771-015-2715-3
[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time
experiment investigations on the coupled thermomechanical
and cracking behaviors in granite containing three pre-
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224 106797 DOI 101016jengfracmech2019106797
[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
Experimental study on the influence of temperature on the
mechanical properties of granite under uni-axial compression
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J Cent South Univ (2021) 28 3173-3189
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101016jijrmms201207026
[18] YANG Zhi-qiang Key technology research on the efficient
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559minus566 DOI 101016JENG201704021
[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
Monitoring and mechanisms of ground deformation and
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Jinchuan Mine 2 China [J] Environmental Earth Sciences
2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7
[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
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English 1986 60(3) 91minus106 DOI 101111j1755-6724
1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
İ Utilization of industrial waste products as pozzolanic
material in cemented paste backfill of high sulphide mill
tailings [J] Journal of Hazardous Materials 2009 168(2 3)
848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
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International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
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[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
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(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
and ore-backfill coupling structure under highhorizontal stress and 2) The exploration of theinfluence of shear direction on the shearperformance of ore-backfill coupling structure Thefindings presented in this paper provide some basisfor safety evaluation and design of deep backfillstopes
2 Experimental set-up
21 MaterialsThe rod-mill sand (RMS) was used in this
study derived from the sand silo of the backfillplant on the surface in Jinchuan No 2 mineAccording to the main physicochemical propertiesof test results as shown in Tables 1 2 and Figure 1the coefficient of uniformity and coefficient ofcurvature of RMS are 17226 and 1184respectively indicating that the RMS is well-gradedThe RMS contains high silica content (exceed 70)and low sulfur content which is conducive toimproving the strength of cemented backfill[21 22] The Jinchang Portland cement (JPC)produced by a local cement plant in Jinchang was
used as the hydraulic binder in the experimentalinvestigations The JPC and RMS were blended in aratio of 2080 Tap water in the laboratory was usedto mix the solid mass (total mass of dry RMS andJPC) the pH value of mixing water was 763 andthe mass ratio of water to total solid was 2278
22 Specimen preparationTwo types of cube specimens CRB and OCRB
coupling specimens with a side length of 50 mmwere involved in the experimental study Figure 2shows the specimen preparation procedures indetail 1) The ore was taken from the 1000 m levelof Jinchuan No 2 mine and the average uniaxialcompressive strength (UCS) of intact ore sampleswas 129 MPa The intact ore specimens withdimensions of 50 mmtimes50 mmtimes50 mm wereobtained by using the techniques of cutting andpolishing Then to minimize the processing damageto the ore specimens a computer numerical control(CNC) router was used to carve the square hole (25mmtimes 25 mmtimes50 mm) in the middle of intact orespecimens 2) In the preparation of backfill slurryput the required amount of dry RMS and JPC into amixing container and the solid mass was well-mixed after being stirred for 5 min Then therequired amount of water was added to the containerand stirred for another 10 min until the slurry wasmixed homogeneously Next the slurry can bepoured into the cube dismountable transparentacrylic molds and the hollow section of orespecimens The molds can be removed after waitingfor 12 h for the initial setting at room temperature(20 degC) and then the CRB and OCRB specimenswere cured in a programmable constant temperatureand humidity curing box
A total of 45 specimens including 36 CRB
Table 1 Physical properties of RMS
Parameter
Particle density(g∙cmminus3)
Porosity
D10mm
D30mm
D50mm
D60mm
D90mm
Cu
Cc
RMS
267
4064
0124
0560
1434
2136
2771
17226
1184
Note Di is the particle size at i passing Cu is the coefficient ofuniformity Cu=D60D10 Cc is the coefficient of curvature Cc=D2
30(D10timesD60)
Table 2 Main chemical compositions of RMS and JPC(wt)
Sample
RMS
JPC
SiO2
7147
25
Al2O3
105
758
CaO
441
4992
Na2O
344
057
Sample
RMS
JPC
K2O
297
098
Fe2O3
28
314
MgO
202
234
SO3
113
457
Figure 1 Particle size sieving results of RMS
3175
J Cent South Univ (2021) 28 3173-3189
specimens and 9 OCRB specimens were prepared
using the procedures mentioned above Thereinto
the CRB specimens were continuously cured for
28 d in a constant temperature (20plusmn05) degC and
constant humidity of (95plusmn1) while the OCRB
specimens were continuously cured for 28 d in a
constant humidity of (95plusmn1) at varioustemperatures (20 40 and 60 deg C) After the curingprocess was completed the laboratory tests can beperformed according to the testing program
23 Testing programThe testing program is shown in Table 3 The
CRB specimens were tested at four various normalstresses (200 300 400 and 500 kPa) while theOCRB specimens were tested at three differentshear directions (D1 along the axis D2perpendicular to the axis D3 perpendicular to theaxial plane) The shear planes of OCRB at differentshear directions consist of ore and backfill (i eCRB) in which D1 and D2 have the same shearplane area (i e the backfill and ore accounted for50 each) while the backfill and ore account for25 and 75 of the shear plane area at D3respectively as shown in Figure 3
24 Testing methodsA RJST-616 shear tester (Developed by
Institute of Rock and Soil Mechanics ChineseAcademy of Sciences China) was employed tostudy the shear behavior of CRB and OCRBspecimens In the shear test the force-control modewas first used to load the normal force to a specifiedvalue and keep it constant Then the displacement-control mode was adopted to load the shear force ata rate of 03 mmmin and the test was stoppedautomatically when the shear displacement reached8 mm During the shear tests a PAC-DISP systemwas adopted to collect the AE signals and at leastone Nano-30 miniature AE sensor was mounted atthe surface of the lower part of the tested specimens(as shown in Figure 4(d)) The coupling agent wasapplied between the sensor and the specimen the
Figure 2 Specimen preparation procedures of CRB andOCRB specimensin detail
Table 3 Laboratory testing program of CRB and OCRB specimens under different conditions
Specimen type
CRB
OCRB
Age timed
28
28
28
28
28
28
TemperaturedegC
20
40
60
20
40
60
Normal stresskPa
200 300 400 500
200 300 400 500
200 300 400 500
500
500
500
Shear direction
mdash
mdash
mdash
D1D2D3
Parameter
PSSRSS
AE Signal
PSSAE Signal
Note All specimens were cured at constant humility of (95plusmn1) D1 is the direction along the axis D2 is the direction perpendicular to theaxis D3 is the direction perpendicular to the axial plane
3176
J Cent South Univ (2021) 28 3173-3189
pre-amplification was set to 40 dB and the AE
detection threshold was fixed at 45 dB and the
acquisition rate of AE signals was set to 1 MSPS
The direct shear tester and AE acquisition system
are shown in Figure 4
As a common non-destructive testing (NDT)
technology in the field of geotechnical engineering
the AE technology can be used to analyze the
cracking process of rock [23minus26] Cracking process
analysis based on AE technology involves a variety
of related characteristic parameters such as hit
event rate count frequency and energy among
which the hitevent rate and AE energy rate are
often considered as the critical parameters in
the shear failure process analysis [27minus29] The AE
energy released during the shear failure process can
Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3
3177
J Cent South Univ (2021) 28 3173-3189
be calculated with the following equations [30 31]
Ei =1R intti
tj
U 2 ( t )dt (1)
E =sumEi (2)
where R is the input impedance of voltage
measurement ti and tj are the beginning and ending
time of AE event segment respectively Ei is the
absolute energy obtained by the AE probe during
the time of tj minus ti U(t) is the voltage value of AE
event related to the time t E is the total absolute
energy during the whole shearing process
3 Experimental results and analysis
31 Temperature effect on shear mechanical and
microstructure properties of CRB
311 Shear cracking processes
Figure 5 shows the relationship between shear
stress and shear displacement of CRB at various
temperatures The results indicate that the shear
deformation behaviors at different temperatures are
consistent and in general they can be divided into
four stages initial compaction stage (I) pre-peak
elastic deformation stage (II) post-peak plastic
deformation stage (III) residual deformation
stage (IV) In stage I the shear stress increases
slowly with the shear displacement due to the
contact gap between specimen and shear box and
voids inside the CRB In stage II the shear stress
increases rapidly and linearly with the shear
displacement until it reaches the peak shear strength
(PSS) and in general the PSS can be achieved
within the range of 1minus3 mm shear displacement The
shear stress decreases gently with the shear
displacement in stage III and tends to be stable after
Figure 4 Direct shear tester and AE acquisition system
Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures
3178
J Cent South Univ (2021) 28 3173-3189
entering stage IV With the increase of temperature
(e g from 20 to 40 ordmC) the PSS and peak shear
displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]
To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the
residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage
Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The
Figure 6 AE hit response during shear test of CRB at20 degC
Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC
3179
J Cent South Univ (2021) 28 3173-3189
higher the temperature the more concentrated theenergy release For example the interval length of
shear displacement of AE energy released at 20 ordmC
is 54 mm while those at 40 and 60 ordmC are 35 and
23 mm respectively After entering the stable
period the cumulative AE energy of 20 40 and
60 ordmC are 1592times106 857times106 and 2218times106 aJ
respectively indicating that the energy release of
CRB during the shear failure process at 40 ordmC is
gentle while that at 60 ordmC is stronger
312 Shear strength parameters
Figure 8 shows the test results of shear strength
parameters of CRB at various temperatures
indicating that the temperature has a significant
influence on both peak shear strength (PSS) and
residual shear strength (RSS) of CRB The
temperature can have a positive effect on the PSS
while it may have a negative impact on RSS For
example the RSS at 40 and 60 ordmC is lower than that
at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8
under the same conditions Besides the shear
strength and normal stress at various temperatures
are in a good linear relationship and the correlation
coefficient R2 of linear fitting is all greater than
092 Therefore it can be considered that the shear
failure of CRB at various temperatures meets
the Mohr-Coulomb criterion [34minus36] and strength
criterion formulas are as follows
τp = cp + σn tanϕp (3)
τr = cr + σn tanϕr (4)
where τp and τr are peak shear strength and residual
shear strength respectively cp and cr are peak
cohesion and residual cohesion respectively ϕp and
ϕr are peak angle of internal friction and residual
angle of internal friction respectively σn is the
normal stress
Table 4 shows the calculation results of the
peak shear strength and shear strength parameters at
various temperatures according to Eqs (3) and (4)
The peak cohesion cp ranges from 145012 to
155821 kPa and it is positively correlated with the
temperature The peak angle of internal friction ϕp is
between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)
The residual cohesion cr ranges from 8053 to
4048 kPa and the maximum cr value is at 40 ordmC
The residual angle of internal friction ϕr is between
Table 4 Linear fitting results of shear strength parameters of CRB
Group
I
II
III
TemperaturedegC
20
40
60
Peak strength parameter
Fitting formula
y1= 145012+115x1
y2= 154614+105x2
y3= 155821+116x3
Correlationcoefficient
R2
0923
0952
0990
CohesioncpkPa
145012
154614
155821
Internalfrictionangleϕp(deg)
4899
4640
4924
Residual strength parameter
Fitting formula
y1=4602+102x1
y2=8053+075x2
y3=4048+096x3
Correlationcoefficient
R2
0999
0978
0975
CohesioncrkPa
4602
8053
4048
Internalfrictionangleϕr(deg)
4557
3687
4383
Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS
3180
J Cent South Univ (2021) 28 3173-3189
3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
3181
J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
3182
J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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[9] CUI Liang FALL M Mechanical and thermal properties of
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[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei
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[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI
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[12] NASIR O FALL M Coupling binder hydration temperature
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[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A
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[14] FALL M POKHAREL M Coupled effects of sulphate and
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and Concrete Composites 2010 32(10) 819minus828 DOI 10
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[15] WU Di CAI Si-jing Coupled effect of cement hydration and
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1956minus1964 DOI 101007s11771-015-2715-3
[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time
experiment investigations on the coupled thermomechanical
and cracking behaviors in granite containing three pre-
existing fissures [J] Engineering Fracture Mechanics 2020
224 106797 DOI 101016jengfracmech2019106797
[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
Experimental study on the influence of temperature on the
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and fatigue loading [J] International Journal of Rock
Mechanics and Mining Sciences 2012 56 62minus66 DOI
101016jijrmms201207026
[18] YANG Zhi-qiang Key technology research on the efficient
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the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)
559minus566 DOI 101016JENG201704021
[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
Monitoring and mechanisms of ground deformation and
ground fissures induced by cut-and-fill mining in the
Jinchuan Mine 2 China [J] Environmental Earth Sciences
2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7
[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
distribution in Southern China [J] Acta Geologica Sinica-
English 1986 60(3) 91minus106 DOI 101111j1755-6724
1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
İ Utilization of industrial waste products as pozzolanic
material in cemented paste backfill of high sulphide mill
tailings [J] Journal of Hazardous Materials 2009 168(2 3)
848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
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1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
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J Cent South Univ (2021) 28 3173-3189
specimens and 9 OCRB specimens were prepared
using the procedures mentioned above Thereinto
the CRB specimens were continuously cured for
28 d in a constant temperature (20plusmn05) degC and
constant humidity of (95plusmn1) while the OCRB
specimens were continuously cured for 28 d in a
constant humidity of (95plusmn1) at varioustemperatures (20 40 and 60 deg C) After the curingprocess was completed the laboratory tests can beperformed according to the testing program
23 Testing programThe testing program is shown in Table 3 The
CRB specimens were tested at four various normalstresses (200 300 400 and 500 kPa) while theOCRB specimens were tested at three differentshear directions (D1 along the axis D2perpendicular to the axis D3 perpendicular to theaxial plane) The shear planes of OCRB at differentshear directions consist of ore and backfill (i eCRB) in which D1 and D2 have the same shearplane area (i e the backfill and ore accounted for50 each) while the backfill and ore account for25 and 75 of the shear plane area at D3respectively as shown in Figure 3
24 Testing methodsA RJST-616 shear tester (Developed by
Institute of Rock and Soil Mechanics ChineseAcademy of Sciences China) was employed tostudy the shear behavior of CRB and OCRBspecimens In the shear test the force-control modewas first used to load the normal force to a specifiedvalue and keep it constant Then the displacement-control mode was adopted to load the shear force ata rate of 03 mmmin and the test was stoppedautomatically when the shear displacement reached8 mm During the shear tests a PAC-DISP systemwas adopted to collect the AE signals and at leastone Nano-30 miniature AE sensor was mounted atthe surface of the lower part of the tested specimens(as shown in Figure 4(d)) The coupling agent wasapplied between the sensor and the specimen the
Figure 2 Specimen preparation procedures of CRB andOCRB specimensin detail
Table 3 Laboratory testing program of CRB and OCRB specimens under different conditions
Specimen type
CRB
OCRB
Age timed
28
28
28
28
28
28
TemperaturedegC
20
40
60
20
40
60
Normal stresskPa
200 300 400 500
200 300 400 500
200 300 400 500
500
500
500
Shear direction
mdash
mdash
mdash
D1D2D3
Parameter
PSSRSS
AE Signal
PSSAE Signal
Note All specimens were cured at constant humility of (95plusmn1) D1 is the direction along the axis D2 is the direction perpendicular to theaxis D3 is the direction perpendicular to the axial plane
3176
J Cent South Univ (2021) 28 3173-3189
pre-amplification was set to 40 dB and the AE
detection threshold was fixed at 45 dB and the
acquisition rate of AE signals was set to 1 MSPS
The direct shear tester and AE acquisition system
are shown in Figure 4
As a common non-destructive testing (NDT)
technology in the field of geotechnical engineering
the AE technology can be used to analyze the
cracking process of rock [23minus26] Cracking process
analysis based on AE technology involves a variety
of related characteristic parameters such as hit
event rate count frequency and energy among
which the hitevent rate and AE energy rate are
often considered as the critical parameters in
the shear failure process analysis [27minus29] The AE
energy released during the shear failure process can
Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3
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J Cent South Univ (2021) 28 3173-3189
be calculated with the following equations [30 31]
Ei =1R intti
tj
U 2 ( t )dt (1)
E =sumEi (2)
where R is the input impedance of voltage
measurement ti and tj are the beginning and ending
time of AE event segment respectively Ei is the
absolute energy obtained by the AE probe during
the time of tj minus ti U(t) is the voltage value of AE
event related to the time t E is the total absolute
energy during the whole shearing process
3 Experimental results and analysis
31 Temperature effect on shear mechanical and
microstructure properties of CRB
311 Shear cracking processes
Figure 5 shows the relationship between shear
stress and shear displacement of CRB at various
temperatures The results indicate that the shear
deformation behaviors at different temperatures are
consistent and in general they can be divided into
four stages initial compaction stage (I) pre-peak
elastic deformation stage (II) post-peak plastic
deformation stage (III) residual deformation
stage (IV) In stage I the shear stress increases
slowly with the shear displacement due to the
contact gap between specimen and shear box and
voids inside the CRB In stage II the shear stress
increases rapidly and linearly with the shear
displacement until it reaches the peak shear strength
(PSS) and in general the PSS can be achieved
within the range of 1minus3 mm shear displacement The
shear stress decreases gently with the shear
displacement in stage III and tends to be stable after
Figure 4 Direct shear tester and AE acquisition system
Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures
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J Cent South Univ (2021) 28 3173-3189
entering stage IV With the increase of temperature
(e g from 20 to 40 ordmC) the PSS and peak shear
displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]
To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the
residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage
Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The
Figure 6 AE hit response during shear test of CRB at20 degC
Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC
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J Cent South Univ (2021) 28 3173-3189
higher the temperature the more concentrated theenergy release For example the interval length of
shear displacement of AE energy released at 20 ordmC
is 54 mm while those at 40 and 60 ordmC are 35 and
23 mm respectively After entering the stable
period the cumulative AE energy of 20 40 and
60 ordmC are 1592times106 857times106 and 2218times106 aJ
respectively indicating that the energy release of
CRB during the shear failure process at 40 ordmC is
gentle while that at 60 ordmC is stronger
312 Shear strength parameters
Figure 8 shows the test results of shear strength
parameters of CRB at various temperatures
indicating that the temperature has a significant
influence on both peak shear strength (PSS) and
residual shear strength (RSS) of CRB The
temperature can have a positive effect on the PSS
while it may have a negative impact on RSS For
example the RSS at 40 and 60 ordmC is lower than that
at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8
under the same conditions Besides the shear
strength and normal stress at various temperatures
are in a good linear relationship and the correlation
coefficient R2 of linear fitting is all greater than
092 Therefore it can be considered that the shear
failure of CRB at various temperatures meets
the Mohr-Coulomb criterion [34minus36] and strength
criterion formulas are as follows
τp = cp + σn tanϕp (3)
τr = cr + σn tanϕr (4)
where τp and τr are peak shear strength and residual
shear strength respectively cp and cr are peak
cohesion and residual cohesion respectively ϕp and
ϕr are peak angle of internal friction and residual
angle of internal friction respectively σn is the
normal stress
Table 4 shows the calculation results of the
peak shear strength and shear strength parameters at
various temperatures according to Eqs (3) and (4)
The peak cohesion cp ranges from 145012 to
155821 kPa and it is positively correlated with the
temperature The peak angle of internal friction ϕp is
between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)
The residual cohesion cr ranges from 8053 to
4048 kPa and the maximum cr value is at 40 ordmC
The residual angle of internal friction ϕr is between
Table 4 Linear fitting results of shear strength parameters of CRB
Group
I
II
III
TemperaturedegC
20
40
60
Peak strength parameter
Fitting formula
y1= 145012+115x1
y2= 154614+105x2
y3= 155821+116x3
Correlationcoefficient
R2
0923
0952
0990
CohesioncpkPa
145012
154614
155821
Internalfrictionangleϕp(deg)
4899
4640
4924
Residual strength parameter
Fitting formula
y1=4602+102x1
y2=8053+075x2
y3=4048+096x3
Correlationcoefficient
R2
0999
0978
0975
CohesioncrkPa
4602
8053
4048
Internalfrictionangleϕr(deg)
4557
3687
4383
Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS
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J Cent South Univ (2021) 28 3173-3189
3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
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J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
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J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
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J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
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J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
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(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
pre-amplification was set to 40 dB and the AE
detection threshold was fixed at 45 dB and the
acquisition rate of AE signals was set to 1 MSPS
The direct shear tester and AE acquisition system
are shown in Figure 4
As a common non-destructive testing (NDT)
technology in the field of geotechnical engineering
the AE technology can be used to analyze the
cracking process of rock [23minus26] Cracking process
analysis based on AE technology involves a variety
of related characteristic parameters such as hit
event rate count frequency and energy among
which the hitevent rate and AE energy rate are
often considered as the critical parameters in
the shear failure process analysis [27minus29] The AE
energy released during the shear failure process can
Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3
3177
J Cent South Univ (2021) 28 3173-3189
be calculated with the following equations [30 31]
Ei =1R intti
tj
U 2 ( t )dt (1)
E =sumEi (2)
where R is the input impedance of voltage
measurement ti and tj are the beginning and ending
time of AE event segment respectively Ei is the
absolute energy obtained by the AE probe during
the time of tj minus ti U(t) is the voltage value of AE
event related to the time t E is the total absolute
energy during the whole shearing process
3 Experimental results and analysis
31 Temperature effect on shear mechanical and
microstructure properties of CRB
311 Shear cracking processes
Figure 5 shows the relationship between shear
stress and shear displacement of CRB at various
temperatures The results indicate that the shear
deformation behaviors at different temperatures are
consistent and in general they can be divided into
four stages initial compaction stage (I) pre-peak
elastic deformation stage (II) post-peak plastic
deformation stage (III) residual deformation
stage (IV) In stage I the shear stress increases
slowly with the shear displacement due to the
contact gap between specimen and shear box and
voids inside the CRB In stage II the shear stress
increases rapidly and linearly with the shear
displacement until it reaches the peak shear strength
(PSS) and in general the PSS can be achieved
within the range of 1minus3 mm shear displacement The
shear stress decreases gently with the shear
displacement in stage III and tends to be stable after
Figure 4 Direct shear tester and AE acquisition system
Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures
3178
J Cent South Univ (2021) 28 3173-3189
entering stage IV With the increase of temperature
(e g from 20 to 40 ordmC) the PSS and peak shear
displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]
To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the
residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage
Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The
Figure 6 AE hit response during shear test of CRB at20 degC
Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC
3179
J Cent South Univ (2021) 28 3173-3189
higher the temperature the more concentrated theenergy release For example the interval length of
shear displacement of AE energy released at 20 ordmC
is 54 mm while those at 40 and 60 ordmC are 35 and
23 mm respectively After entering the stable
period the cumulative AE energy of 20 40 and
60 ordmC are 1592times106 857times106 and 2218times106 aJ
respectively indicating that the energy release of
CRB during the shear failure process at 40 ordmC is
gentle while that at 60 ordmC is stronger
312 Shear strength parameters
Figure 8 shows the test results of shear strength
parameters of CRB at various temperatures
indicating that the temperature has a significant
influence on both peak shear strength (PSS) and
residual shear strength (RSS) of CRB The
temperature can have a positive effect on the PSS
while it may have a negative impact on RSS For
example the RSS at 40 and 60 ordmC is lower than that
at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8
under the same conditions Besides the shear
strength and normal stress at various temperatures
are in a good linear relationship and the correlation
coefficient R2 of linear fitting is all greater than
092 Therefore it can be considered that the shear
failure of CRB at various temperatures meets
the Mohr-Coulomb criterion [34minus36] and strength
criterion formulas are as follows
τp = cp + σn tanϕp (3)
τr = cr + σn tanϕr (4)
where τp and τr are peak shear strength and residual
shear strength respectively cp and cr are peak
cohesion and residual cohesion respectively ϕp and
ϕr are peak angle of internal friction and residual
angle of internal friction respectively σn is the
normal stress
Table 4 shows the calculation results of the
peak shear strength and shear strength parameters at
various temperatures according to Eqs (3) and (4)
The peak cohesion cp ranges from 145012 to
155821 kPa and it is positively correlated with the
temperature The peak angle of internal friction ϕp is
between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)
The residual cohesion cr ranges from 8053 to
4048 kPa and the maximum cr value is at 40 ordmC
The residual angle of internal friction ϕr is between
Table 4 Linear fitting results of shear strength parameters of CRB
Group
I
II
III
TemperaturedegC
20
40
60
Peak strength parameter
Fitting formula
y1= 145012+115x1
y2= 154614+105x2
y3= 155821+116x3
Correlationcoefficient
R2
0923
0952
0990
CohesioncpkPa
145012
154614
155821
Internalfrictionangleϕp(deg)
4899
4640
4924
Residual strength parameter
Fitting formula
y1=4602+102x1
y2=8053+075x2
y3=4048+096x3
Correlationcoefficient
R2
0999
0978
0975
CohesioncrkPa
4602
8053
4048
Internalfrictionangleϕr(deg)
4557
3687
4383
Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS
3180
J Cent South Univ (2021) 28 3173-3189
3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
3181
J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
3182
J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
3183
J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
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[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
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[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
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[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
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[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
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[39] BERNIER R L LI M G MOERMAN A Effects of tailings
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[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
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[41] LI Wen-chen FALL M Sulphate effect on the early age
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[42] SHANG J ZHAO Z MA S On the shear failure of incipient
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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
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(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
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J Cent South Univ (2021) 28 3173-3189
be calculated with the following equations [30 31]
Ei =1R intti
tj
U 2 ( t )dt (1)
E =sumEi (2)
where R is the input impedance of voltage
measurement ti and tj are the beginning and ending
time of AE event segment respectively Ei is the
absolute energy obtained by the AE probe during
the time of tj minus ti U(t) is the voltage value of AE
event related to the time t E is the total absolute
energy during the whole shearing process
3 Experimental results and analysis
31 Temperature effect on shear mechanical and
microstructure properties of CRB
311 Shear cracking processes
Figure 5 shows the relationship between shear
stress and shear displacement of CRB at various
temperatures The results indicate that the shear
deformation behaviors at different temperatures are
consistent and in general they can be divided into
four stages initial compaction stage (I) pre-peak
elastic deformation stage (II) post-peak plastic
deformation stage (III) residual deformation
stage (IV) In stage I the shear stress increases
slowly with the shear displacement due to the
contact gap between specimen and shear box and
voids inside the CRB In stage II the shear stress
increases rapidly and linearly with the shear
displacement until it reaches the peak shear strength
(PSS) and in general the PSS can be achieved
within the range of 1minus3 mm shear displacement The
shear stress decreases gently with the shear
displacement in stage III and tends to be stable after
Figure 4 Direct shear tester and AE acquisition system
Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures
3178
J Cent South Univ (2021) 28 3173-3189
entering stage IV With the increase of temperature
(e g from 20 to 40 ordmC) the PSS and peak shear
displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]
To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the
residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage
Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The
Figure 6 AE hit response during shear test of CRB at20 degC
Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC
3179
J Cent South Univ (2021) 28 3173-3189
higher the temperature the more concentrated theenergy release For example the interval length of
shear displacement of AE energy released at 20 ordmC
is 54 mm while those at 40 and 60 ordmC are 35 and
23 mm respectively After entering the stable
period the cumulative AE energy of 20 40 and
60 ordmC are 1592times106 857times106 and 2218times106 aJ
respectively indicating that the energy release of
CRB during the shear failure process at 40 ordmC is
gentle while that at 60 ordmC is stronger
312 Shear strength parameters
Figure 8 shows the test results of shear strength
parameters of CRB at various temperatures
indicating that the temperature has a significant
influence on both peak shear strength (PSS) and
residual shear strength (RSS) of CRB The
temperature can have a positive effect on the PSS
while it may have a negative impact on RSS For
example the RSS at 40 and 60 ordmC is lower than that
at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8
under the same conditions Besides the shear
strength and normal stress at various temperatures
are in a good linear relationship and the correlation
coefficient R2 of linear fitting is all greater than
092 Therefore it can be considered that the shear
failure of CRB at various temperatures meets
the Mohr-Coulomb criterion [34minus36] and strength
criterion formulas are as follows
τp = cp + σn tanϕp (3)
τr = cr + σn tanϕr (4)
where τp and τr are peak shear strength and residual
shear strength respectively cp and cr are peak
cohesion and residual cohesion respectively ϕp and
ϕr are peak angle of internal friction and residual
angle of internal friction respectively σn is the
normal stress
Table 4 shows the calculation results of the
peak shear strength and shear strength parameters at
various temperatures according to Eqs (3) and (4)
The peak cohesion cp ranges from 145012 to
155821 kPa and it is positively correlated with the
temperature The peak angle of internal friction ϕp is
between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)
The residual cohesion cr ranges from 8053 to
4048 kPa and the maximum cr value is at 40 ordmC
The residual angle of internal friction ϕr is between
Table 4 Linear fitting results of shear strength parameters of CRB
Group
I
II
III
TemperaturedegC
20
40
60
Peak strength parameter
Fitting formula
y1= 145012+115x1
y2= 154614+105x2
y3= 155821+116x3
Correlationcoefficient
R2
0923
0952
0990
CohesioncpkPa
145012
154614
155821
Internalfrictionangleϕp(deg)
4899
4640
4924
Residual strength parameter
Fitting formula
y1=4602+102x1
y2=8053+075x2
y3=4048+096x3
Correlationcoefficient
R2
0999
0978
0975
CohesioncrkPa
4602
8053
4048
Internalfrictionangleϕr(deg)
4557
3687
4383
Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS
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J Cent South Univ (2021) 28 3173-3189
3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
3181
J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
3182
J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei
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[12] NASIR O FALL M Coupling binder hydration temperature
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[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A
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[14] FALL M POKHAREL M Coupled effects of sulphate and
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[15] WU Di CAI Si-jing Coupled effect of cement hydration and
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[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time
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224 106797 DOI 101016jengfracmech2019106797
[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
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[18] YANG Zhi-qiang Key technology research on the efficient
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[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
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[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
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1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
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848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
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[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
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06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
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techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
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[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
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2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
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emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
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[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
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[36] LI Li Generalized solution for mining backfill design [J]
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04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
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2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
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[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
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[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
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[41] LI Wen-chen FALL M Sulphate effect on the early age
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[42] SHANG J ZHAO Z MA S On the shear failure of incipient
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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
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(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
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J Cent South Univ (2021) 28 3173-3189
entering stage IV With the increase of temperature
(e g from 20 to 40 ordmC) the PSS and peak shear
displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]
To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the
residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage
Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The
Figure 6 AE hit response during shear test of CRB at20 degC
Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC
3179
J Cent South Univ (2021) 28 3173-3189
higher the temperature the more concentrated theenergy release For example the interval length of
shear displacement of AE energy released at 20 ordmC
is 54 mm while those at 40 and 60 ordmC are 35 and
23 mm respectively After entering the stable
period the cumulative AE energy of 20 40 and
60 ordmC are 1592times106 857times106 and 2218times106 aJ
respectively indicating that the energy release of
CRB during the shear failure process at 40 ordmC is
gentle while that at 60 ordmC is stronger
312 Shear strength parameters
Figure 8 shows the test results of shear strength
parameters of CRB at various temperatures
indicating that the temperature has a significant
influence on both peak shear strength (PSS) and
residual shear strength (RSS) of CRB The
temperature can have a positive effect on the PSS
while it may have a negative impact on RSS For
example the RSS at 40 and 60 ordmC is lower than that
at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8
under the same conditions Besides the shear
strength and normal stress at various temperatures
are in a good linear relationship and the correlation
coefficient R2 of linear fitting is all greater than
092 Therefore it can be considered that the shear
failure of CRB at various temperatures meets
the Mohr-Coulomb criterion [34minus36] and strength
criterion formulas are as follows
τp = cp + σn tanϕp (3)
τr = cr + σn tanϕr (4)
where τp and τr are peak shear strength and residual
shear strength respectively cp and cr are peak
cohesion and residual cohesion respectively ϕp and
ϕr are peak angle of internal friction and residual
angle of internal friction respectively σn is the
normal stress
Table 4 shows the calculation results of the
peak shear strength and shear strength parameters at
various temperatures according to Eqs (3) and (4)
The peak cohesion cp ranges from 145012 to
155821 kPa and it is positively correlated with the
temperature The peak angle of internal friction ϕp is
between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)
The residual cohesion cr ranges from 8053 to
4048 kPa and the maximum cr value is at 40 ordmC
The residual angle of internal friction ϕr is between
Table 4 Linear fitting results of shear strength parameters of CRB
Group
I
II
III
TemperaturedegC
20
40
60
Peak strength parameter
Fitting formula
y1= 145012+115x1
y2= 154614+105x2
y3= 155821+116x3
Correlationcoefficient
R2
0923
0952
0990
CohesioncpkPa
145012
154614
155821
Internalfrictionangleϕp(deg)
4899
4640
4924
Residual strength parameter
Fitting formula
y1=4602+102x1
y2=8053+075x2
y3=4048+096x3
Correlationcoefficient
R2
0999
0978
0975
CohesioncrkPa
4602
8053
4048
Internalfrictionangleϕr(deg)
4557
3687
4383
Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS
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J Cent South Univ (2021) 28 3173-3189
3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
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J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
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J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
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J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
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J Cent South Univ (2021) 28 3173-3189
higher the temperature the more concentrated theenergy release For example the interval length of
shear displacement of AE energy released at 20 ordmC
is 54 mm while those at 40 and 60 ordmC are 35 and
23 mm respectively After entering the stable
period the cumulative AE energy of 20 40 and
60 ordmC are 1592times106 857times106 and 2218times106 aJ
respectively indicating that the energy release of
CRB during the shear failure process at 40 ordmC is
gentle while that at 60 ordmC is stronger
312 Shear strength parameters
Figure 8 shows the test results of shear strength
parameters of CRB at various temperatures
indicating that the temperature has a significant
influence on both peak shear strength (PSS) and
residual shear strength (RSS) of CRB The
temperature can have a positive effect on the PSS
while it may have a negative impact on RSS For
example the RSS at 40 and 60 ordmC is lower than that
at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8
under the same conditions Besides the shear
strength and normal stress at various temperatures
are in a good linear relationship and the correlation
coefficient R2 of linear fitting is all greater than
092 Therefore it can be considered that the shear
failure of CRB at various temperatures meets
the Mohr-Coulomb criterion [34minus36] and strength
criterion formulas are as follows
τp = cp + σn tanϕp (3)
τr = cr + σn tanϕr (4)
where τp and τr are peak shear strength and residual
shear strength respectively cp and cr are peak
cohesion and residual cohesion respectively ϕp and
ϕr are peak angle of internal friction and residual
angle of internal friction respectively σn is the
normal stress
Table 4 shows the calculation results of the
peak shear strength and shear strength parameters at
various temperatures according to Eqs (3) and (4)
The peak cohesion cp ranges from 145012 to
155821 kPa and it is positively correlated with the
temperature The peak angle of internal friction ϕp is
between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)
The residual cohesion cr ranges from 8053 to
4048 kPa and the maximum cr value is at 40 ordmC
The residual angle of internal friction ϕr is between
Table 4 Linear fitting results of shear strength parameters of CRB
Group
I
II
III
TemperaturedegC
20
40
60
Peak strength parameter
Fitting formula
y1= 145012+115x1
y2= 154614+105x2
y3= 155821+116x3
Correlationcoefficient
R2
0923
0952
0990
CohesioncpkPa
145012
154614
155821
Internalfrictionangleϕp(deg)
4899
4640
4924
Residual strength parameter
Fitting formula
y1=4602+102x1
y2=8053+075x2
y3=4048+096x3
Correlationcoefficient
R2
0999
0978
0975
CohesioncrkPa
4602
8053
4048
Internalfrictionangleϕr(deg)
4557
3687
4383
Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS
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J Cent South Univ (2021) 28 3173-3189
3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
3181
J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
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J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
3188
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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures
To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good
32 Temperature effect on coupling shear
behavior of OCRB
321 Coupling shear deformation and strength
Figure 10 shows the relationship between shear
stress and shear displacement of OCRB at various
temperatures The results show that the shear
deformation behaviors of OCRB at various
temperatures are consistent and can be roughly
Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test
TemperaturedegC
20
40
60
Mass fraction
Quartz
4037
3284
3864
Microcline maximum
1923
2298
1079
Albite
1765
2217
2523
Illite
1052
771
1182
Portlandite
137
555
206
Calcite
626
515
586
Ettringite
409
289
399
Dolomite
051
07
16
Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC
3181
J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
3182
J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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Effect of sulfide on the long-term strength of lead-zinc
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(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
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J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
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J Cent South Univ (2021) 28 3173-3189
divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation
stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively
Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation
Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)
Table 6 Test results of shear strength and AE parameters of OCRB
Specimen ID
OCRB-20-1
OCRB-40-1
OCRB-60-1
OCRB-20-2
OCRB-40-2
OCRB-60-2
OCRB-20-3
OCRB-40-3
OCRB-60-3
TemperatureordmC
20
40
60
20
40
60
20
40
60
Sheardirection
D1
D1
D1
D2
D2
D2
D3
D3
D3
Shear planesize(mmtimesmm)
5080times5068
5040times5090
5088times5060
5020times5030
5062times5100
5082times5060
5070times5090
5060times5060
5038times5072
Peak sheardisplacement
mm
18167
21619
19039
23104
20686
14476
20741
20902
24096
Peak shearstrengthkPa
531279
771627
546236
333220
374339
328642
563351
487432
925967
Residualshear strength
kPa
40124
50909
61021
62929
91144
95898
72075
72334
74708
AE signaldurations
1388
1650
1643
1886
1498
1560
1938
1488
1435
CumulativeAE energy
106 aJ
1881
80306
22545
6890
1757
12321
3704
12351
87744
3182
J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
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J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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Experimental study on the influence of temperature on the
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Ji-yang Basic characteristics of the earth1049011s temperature
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1986mp60003008x
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material in cemented paste backfill of high sulphide mill
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848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
3188
J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process
Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic
parameters with temperature during the shear
process are similar With the increase of
temperature the response of AE hit rate and count
rate is significantly enhanced and peak frequency
gradually develops from low frequency to high
frequency Besides the cumulative AE hit and AE
count during the shear process at 20 degC are generally
at a low level and the values are significantly
increased with the temperature increased to 40 or
60 deg C indicating that the temperature can
substantially intensify AE activity during the shear
process The main reason is that the temperature canaffect the mechanical properties of backfill and the
structural characteristics of ore-backfill coupling
specimens (e g ore-backfill interface parameters)
thus affecting the mechanical response of the shear
process
Figure 13 shows the experimental curves of the
temperature effect on the AE energy characteristic
parameters during the shear failure process of
OCRB The results suggest that the AE energy has a
good correlation with the shear deformation of
OCRB and the variation characteristics are similar
to that of CRB that is it will also go through three
periods of the initial quiet period rising period and
stable period Compared with CRB the AE energy
Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS
Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1
3183
J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
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[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI
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[12] NASIR O FALL M Coupling binder hydration temperature
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[14] FALL M POKHAREL M Coupled effects of sulphate and
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and Concrete Composites 2010 32(10) 819minus828 DOI 10
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[15] WU Di CAI Si-jing Coupled effect of cement hydration and
temperature on hydraulic behavior of cemented tailings
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1956minus1964 DOI 101007s11771-015-2715-3
[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time
experiment investigations on the coupled thermomechanical
and cracking behaviors in granite containing three pre-
existing fissures [J] Engineering Fracture Mechanics 2020
224 106797 DOI 101016jengfracmech2019106797
[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
Experimental study on the influence of temperature on the
mechanical properties of granite under uni-axial compression
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and fatigue loading [J] International Journal of Rock
Mechanics and Mining Sciences 2012 56 62minus66 DOI
101016jijrmms201207026
[18] YANG Zhi-qiang Key technology research on the efficient
exploitation and comprehensive utilization of resources in
the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)
559minus566 DOI 101016JENG201704021
[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
Monitoring and mechanisms of ground deformation and
ground fissures induced by cut-and-fill mining in the
Jinchuan Mine 2 China [J] Environmental Earth Sciences
2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7
[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
distribution in Southern China [J] Acta Geologica Sinica-
English 1986 60(3) 91minus106 DOI 101111j1755-6724
1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
İ Utilization of industrial waste products as pozzolanic
material in cemented paste backfill of high sulphide mill
tailings [J] Journal of Hazardous Materials 2009 168(2 3)
848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
3188
J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
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J Cent South Univ (2021) 28 3173-3189
of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)
displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest
33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the
shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface
The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after
Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3
3184
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
References
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[2] SHESHPARI M A review of underground mine backfillingmethods with emphasis on cemented paste backfill [J]Electronic Journal of Geotechnical Engineering 201520(13) 5183minus5208
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[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge
201803005
[5] FALL M BENZAAZOUA M SAA E G Mix proportioning
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[6] BELEM T BENZAAZOUA M BUSSIEgraveRE B Mechanical
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[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I
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[8] WANG Yong FALL M WU Ai-xiang Initial temperature-
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[9] CUI Liang FALL M Mechanical and thermal properties of
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[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei
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[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI
Z Temperature dependence of the reactivity of cemented
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[12] NASIR O FALL M Coupling binder hydration temperature
and compressive strength development of underground
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Underground Space Technology 2010 25(1) 9 minus 20 DOI
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[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A
contribution to understanding the effects of curing
temperature on the mechanical properties of mine cemented
tailings backfill [J] Engineering Geology 2010 114(3 4)
397minus413 DOI 101016jenggeo201005016
[14] FALL M POKHAREL M Coupled effects of sulphate and
temperature on the strength development of cemented
tailings backfills Portland cement-paste backfill [J] Cement
and Concrete Composites 2010 32(10) 819minus828 DOI 10
1016jcemconcomp201008002
[15] WU Di CAI Si-jing Coupled effect of cement hydration and
temperature on hydraulic behavior of cemented tailings
backfill [J] Journal of Central South University 2015 22(5)
1956minus1964 DOI 101007s11771-015-2715-3
[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time
experiment investigations on the coupled thermomechanical
and cracking behaviors in granite containing three pre-
existing fissures [J] Engineering Fracture Mechanics 2020
224 106797 DOI 101016jengfracmech2019106797
[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
Experimental study on the influence of temperature on the
mechanical properties of granite under uni-axial compression
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and fatigue loading [J] International Journal of Rock
Mechanics and Mining Sciences 2012 56 62minus66 DOI
101016jijrmms201207026
[18] YANG Zhi-qiang Key technology research on the efficient
exploitation and comprehensive utilization of resources in
the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)
559minus566 DOI 101016JENG201704021
[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
Monitoring and mechanisms of ground deformation and
ground fissures induced by cut-and-fill mining in the
Jinchuan Mine 2 China [J] Environmental Earth Sciences
2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7
[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
distribution in Southern China [J] Acta Geologica Sinica-
English 1986 60(3) 91minus106 DOI 101111j1755-6724
1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
İ Utilization of industrial waste products as pozzolanic
material in cemented paste backfill of high sulphide mill
tailings [J] Journal of Hazardous Materials 2009 168(2 3)
848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
3188
J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)
Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and
lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3
4 Discussion
Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure
Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC
3185
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
References
[1] SUN Wei WANG Hong-jiang HOU Ke-peng Control ofwaste rock-tailings paste backfill for active miningsubsidence areas [J] Journal of Cleaner Production 2018171 567minus579 DOI 101016jjclepro201709253
[2] SHESHPARI M A review of underground mine backfillingmethods with emphasis on cemented paste backfill [J]Electronic Journal of Geotechnical Engineering 201520(13) 5183minus5208
[3] QI Chong-chong FOURIE A Cemented paste backfill formineral tailings management Review and futureperspectives [J] Minerals Engineering 2019 144 106025DOI 101016jmineng2019106025
[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge
201803005
[5] FALL M BENZAAZOUA M SAA E G Mix proportioning
of underground cemented tailings backfill [J] Tunnelling and
Underground Space Technology 2008 23(1) 80minus 90 DOI
101016jtust200608005
[6] BELEM T BENZAAZOUA M BUSSIEgraveRE B Mechanical
behaviour of cemented paste backfill [C] Proc of 53rd
Canadian Geotechnical Conference Montreal 2000
373minus380
[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I
Quantitative investigation on micro-parameters of cemented
paste backfill and its sensitivity analysis [J] Journal of
Central South University 2020 27(1) 267 minus 276 DOI
101007s11771-020-4294-1
[8] WANG Yong FALL M WU Ai-xiang Initial temperature-
dependence of strength development and self-desiccation in
cemented paste backfill that contains sodium silicate [J]
Cement and Concrete Composites 2016 67 101minus110 DOI
101016jcemconcomp201601005
[9] CUI Liang FALL M Mechanical and thermal properties of
cemented tailings materials at early ages Influence of initial
temperature curing stress and drainage conditions [J]
Construction and Building Materials 2016 125 553 minus 563
DOI 101016jconbuildmat201608080
[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei
QIU Jing-ping Ultrasonic evaluation of strength properties
of cemented paste backfill Effects of mineral admixture and
curing temperature [J] Ultrasonics 2020 100 105983 DOI
101016jultras2019105983
[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI
Z Temperature dependence of the reactivity of cemented
paste backfill [J] Applied Geochemistry 2016 72 10minus 19
DOI 101016japgeochem201606005
[12] NASIR O FALL M Coupling binder hydration temperature
and compressive strength development of underground
cemented paste backfill at early ages [J] Tunnelling and
Underground Space Technology 2010 25(1) 9 minus 20 DOI
101016jtust200907008
[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A
contribution to understanding the effects of curing
temperature on the mechanical properties of mine cemented
tailings backfill [J] Engineering Geology 2010 114(3 4)
397minus413 DOI 101016jenggeo201005016
[14] FALL M POKHAREL M Coupled effects of sulphate and
temperature on the strength development of cemented
tailings backfills Portland cement-paste backfill [J] Cement
and Concrete Composites 2010 32(10) 819minus828 DOI 10
1016jcemconcomp201008002
[15] WU Di CAI Si-jing Coupled effect of cement hydration and
temperature on hydraulic behavior of cemented tailings
backfill [J] Journal of Central South University 2015 22(5)
1956minus1964 DOI 101007s11771-015-2715-3
[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time
experiment investigations on the coupled thermomechanical
and cracking behaviors in granite containing three pre-
existing fissures [J] Engineering Fracture Mechanics 2020
224 106797 DOI 101016jengfracmech2019106797
[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
Experimental study on the influence of temperature on the
mechanical properties of granite under uni-axial compression
3187
J Cent South Univ (2021) 28 3173-3189
and fatigue loading [J] International Journal of Rock
Mechanics and Mining Sciences 2012 56 62minus66 DOI
101016jijrmms201207026
[18] YANG Zhi-qiang Key technology research on the efficient
exploitation and comprehensive utilization of resources in
the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)
559minus566 DOI 101016JENG201704021
[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
Monitoring and mechanisms of ground deformation and
ground fissures induced by cut-and-fill mining in the
Jinchuan Mine 2 China [J] Environmental Earth Sciences
2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7
[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
distribution in Southern China [J] Acta Geologica Sinica-
English 1986 60(3) 91minus106 DOI 101111j1755-6724
1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
İ Utilization of industrial waste products as pozzolanic
material in cemented paste backfill of high sulphide mill
tailings [J] Journal of Hazardous Materials 2009 168(2 3)
848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
3188
J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)
Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress
orientation should be taken into consideration in thebackfill mining and stope design
In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research
5 Conclusions
1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good
2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the
3186
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
References
[1] SUN Wei WANG Hong-jiang HOU Ke-peng Control ofwaste rock-tailings paste backfill for active miningsubsidence areas [J] Journal of Cleaner Production 2018171 567minus579 DOI 101016jjclepro201709253
[2] SHESHPARI M A review of underground mine backfillingmethods with emphasis on cemented paste backfill [J]Electronic Journal of Geotechnical Engineering 201520(13) 5183minus5208
[3] QI Chong-chong FOURIE A Cemented paste backfill formineral tailings management Review and futureperspectives [J] Minerals Engineering 2019 144 106025DOI 101016jmineng2019106025
[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge
201803005
[5] FALL M BENZAAZOUA M SAA E G Mix proportioning
of underground cemented tailings backfill [J] Tunnelling and
Underground Space Technology 2008 23(1) 80minus 90 DOI
101016jtust200608005
[6] BELEM T BENZAAZOUA M BUSSIEgraveRE B Mechanical
behaviour of cemented paste backfill [C] Proc of 53rd
Canadian Geotechnical Conference Montreal 2000
373minus380
[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I
Quantitative investigation on micro-parameters of cemented
paste backfill and its sensitivity analysis [J] Journal of
Central South University 2020 27(1) 267 minus 276 DOI
101007s11771-020-4294-1
[8] WANG Yong FALL M WU Ai-xiang Initial temperature-
dependence of strength development and self-desiccation in
cemented paste backfill that contains sodium silicate [J]
Cement and Concrete Composites 2016 67 101minus110 DOI
101016jcemconcomp201601005
[9] CUI Liang FALL M Mechanical and thermal properties of
cemented tailings materials at early ages Influence of initial
temperature curing stress and drainage conditions [J]
Construction and Building Materials 2016 125 553 minus 563
DOI 101016jconbuildmat201608080
[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei
QIU Jing-ping Ultrasonic evaluation of strength properties
of cemented paste backfill Effects of mineral admixture and
curing temperature [J] Ultrasonics 2020 100 105983 DOI
101016jultras2019105983
[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI
Z Temperature dependence of the reactivity of cemented
paste backfill [J] Applied Geochemistry 2016 72 10minus 19
DOI 101016japgeochem201606005
[12] NASIR O FALL M Coupling binder hydration temperature
and compressive strength development of underground
cemented paste backfill at early ages [J] Tunnelling and
Underground Space Technology 2010 25(1) 9 minus 20 DOI
101016jtust200907008
[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A
contribution to understanding the effects of curing
temperature on the mechanical properties of mine cemented
tailings backfill [J] Engineering Geology 2010 114(3 4)
397minus413 DOI 101016jenggeo201005016
[14] FALL M POKHAREL M Coupled effects of sulphate and
temperature on the strength development of cemented
tailings backfills Portland cement-paste backfill [J] Cement
and Concrete Composites 2010 32(10) 819minus828 DOI 10
1016jcemconcomp201008002
[15] WU Di CAI Si-jing Coupled effect of cement hydration and
temperature on hydraulic behavior of cemented tailings
backfill [J] Journal of Central South University 2015 22(5)
1956minus1964 DOI 101007s11771-015-2715-3
[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time
experiment investigations on the coupled thermomechanical
and cracking behaviors in granite containing three pre-
existing fissures [J] Engineering Fracture Mechanics 2020
224 106797 DOI 101016jengfracmech2019106797
[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
Experimental study on the influence of temperature on the
mechanical properties of granite under uni-axial compression
3187
J Cent South Univ (2021) 28 3173-3189
and fatigue loading [J] International Journal of Rock
Mechanics and Mining Sciences 2012 56 62minus66 DOI
101016jijrmms201207026
[18] YANG Zhi-qiang Key technology research on the efficient
exploitation and comprehensive utilization of resources in
the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)
559minus566 DOI 101016JENG201704021
[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
Monitoring and mechanisms of ground deformation and
ground fissures induced by cut-and-fill mining in the
Jinchuan Mine 2 China [J] Environmental Earth Sciences
2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7
[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
distribution in Southern China [J] Acta Geologica Sinica-
English 1986 60(3) 91minus106 DOI 101111j1755-6724
1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
İ Utilization of industrial waste products as pozzolanic
material in cemented paste backfill of high sulphide mill
tailings [J] Journal of Hazardous Materials 2009 168(2 3)
848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
3188
J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors
3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design
ContributorsThe overarching research goals were
developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version
Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI
Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest
References
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[2] SHESHPARI M A review of underground mine backfillingmethods with emphasis on cemented paste backfill [J]Electronic Journal of Geotechnical Engineering 201520(13) 5183minus5208
[3] QI Chong-chong FOURIE A Cemented paste backfill formineral tailings management Review and futureperspectives [J] Minerals Engineering 2019 144 106025DOI 101016jmineng2019106025
[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge
201803005
[5] FALL M BENZAAZOUA M SAA E G Mix proportioning
of underground cemented tailings backfill [J] Tunnelling and
Underground Space Technology 2008 23(1) 80minus 90 DOI
101016jtust200608005
[6] BELEM T BENZAAZOUA M BUSSIEgraveRE B Mechanical
behaviour of cemented paste backfill [C] Proc of 53rd
Canadian Geotechnical Conference Montreal 2000
373minus380
[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I
Quantitative investigation on micro-parameters of cemented
paste backfill and its sensitivity analysis [J] Journal of
Central South University 2020 27(1) 267 minus 276 DOI
101007s11771-020-4294-1
[8] WANG Yong FALL M WU Ai-xiang Initial temperature-
dependence of strength development and self-desiccation in
cemented paste backfill that contains sodium silicate [J]
Cement and Concrete Composites 2016 67 101minus110 DOI
101016jcemconcomp201601005
[9] CUI Liang FALL M Mechanical and thermal properties of
cemented tailings materials at early ages Influence of initial
temperature curing stress and drainage conditions [J]
Construction and Building Materials 2016 125 553 minus 563
DOI 101016jconbuildmat201608080
[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei
QIU Jing-ping Ultrasonic evaluation of strength properties
of cemented paste backfill Effects of mineral admixture and
curing temperature [J] Ultrasonics 2020 100 105983 DOI
101016jultras2019105983
[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI
Z Temperature dependence of the reactivity of cemented
paste backfill [J] Applied Geochemistry 2016 72 10minus 19
DOI 101016japgeochem201606005
[12] NASIR O FALL M Coupling binder hydration temperature
and compressive strength development of underground
cemented paste backfill at early ages [J] Tunnelling and
Underground Space Technology 2010 25(1) 9 minus 20 DOI
101016jtust200907008
[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A
contribution to understanding the effects of curing
temperature on the mechanical properties of mine cemented
tailings backfill [J] Engineering Geology 2010 114(3 4)
397minus413 DOI 101016jenggeo201005016
[14] FALL M POKHAREL M Coupled effects of sulphate and
temperature on the strength development of cemented
tailings backfills Portland cement-paste backfill [J] Cement
and Concrete Composites 2010 32(10) 819minus828 DOI 10
1016jcemconcomp201008002
[15] WU Di CAI Si-jing Coupled effect of cement hydration and
temperature on hydraulic behavior of cemented tailings
backfill [J] Journal of Central South University 2015 22(5)
1956minus1964 DOI 101007s11771-015-2715-3
[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time
experiment investigations on the coupled thermomechanical
and cracking behaviors in granite containing three pre-
existing fissures [J] Engineering Fracture Mechanics 2020
224 106797 DOI 101016jengfracmech2019106797
[17] CHEN You-liang NI Jing SHAO Wei AZZAM R
Experimental study on the influence of temperature on the
mechanical properties of granite under uni-axial compression
3187
J Cent South Univ (2021) 28 3173-3189
and fatigue loading [J] International Journal of Rock
Mechanics and Mining Sciences 2012 56 62minus66 DOI
101016jijrmms201207026
[18] YANG Zhi-qiang Key technology research on the efficient
exploitation and comprehensive utilization of resources in
the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)
559minus566 DOI 101016JENG201704021
[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
Monitoring and mechanisms of ground deformation and
ground fissures induced by cut-and-fill mining in the
Jinchuan Mine 2 China [J] Environmental Earth Sciences
2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7
[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
distribution in Southern China [J] Acta Geologica Sinica-
English 1986 60(3) 91minus106 DOI 101111j1755-6724
1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
İ Utilization of industrial waste products as pozzolanic
material in cemented paste backfill of high sulphide mill
tailings [J] Journal of Hazardous Materials 2009 168(2 3)
848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
3188
J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
and fatigue loading [J] International Journal of Rock
Mechanics and Mining Sciences 2012 56 62minus66 DOI
101016jijrmms201207026
[18] YANG Zhi-qiang Key technology research on the efficient
exploitation and comprehensive utilization of resources in
the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)
559minus566 DOI 101016JENG201704021
[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie
Monitoring and mechanisms of ground deformation and
ground fissures induced by cut-and-fill mining in the
Jinchuan Mine 2 China [J] Environmental Earth Sciences
2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7
[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG
Ji-yang Basic characteristics of the earth1049011s temperature
distribution in Southern China [J] Acta Geologica Sinica-
English 1986 60(3) 91minus106 DOI 101111j1755-6724
1986mp60003008x
[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP
İ Utilization of industrial waste products as pozzolanic
material in cemented paste backfill of high sulphide mill
tailings [J] Journal of Hazardous Materials 2009 168(2 3)
848minus856 DOI 101016jjhazmat200902100
[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo
Effect of sulfide on the long-term strength of lead-zinc
tailings cemented paste backfill [J] Construction and
Building Materials 2019 200 436 minus 446 DOI 101016j
conbuildmat201812069
[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU
Yong Experimental investigation of progressive cracking
processes in granite under uniaxial loading using digital
imaging and AE techniques [J] Journal of Structural
Geology 2019 126 129minus 145 DOI 101016j jsg 2019
06003
[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture
analysis in brittle sandstone by digital imaging and AE
techniques Role of flaw length ratio [J] Journal of Materials
in Civil Engineering 2020 32(5) 04020085 DOI 101061
(asce)mt1943-55330003151
[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi
BERTO F Progressive failure of brittle rocks with non-
isometric flaws Insights from acousto-optic-mechanical
(AOM) data [J] Fatigue amp Fracture of Engineering Materials
amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe
13019
[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate
characteristics of flawed granite From damage stress to
ultimate failure [J] Geophysical Journal International 2020
222(2) 795minus814 DOI 101093gjiggaa207
[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing
the effectiveness of energy and hit rate parameters of
acoustic emission for prediction of rock failure [C] ISRM
International Symposium on Rock Mechanics-SINOROCK
2009 Hong Kong China 2009 ISRM-SINOROCK-
2009-044
[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin
CHENG Guang-tan Shear rate effects on the post-peak shear
behaviour and acoustic emission characteristics of artificially
split granite joints [J] Rock Mechanics and Rock
Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-
018-1722-8
[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting
catastrophic rupture in brittle rocks using precursory AE time
series [J] Journal of Geophysical Research Solid Earth
2020 125(8) e2019JB019276 DOI 1010292019JB019276
[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing
temperature on mechanical performance and acoustic
emission properties of cemented coal gangue-fly ash backfill
[J] Geotechnical and Geological Engineering 2019 37(4)
3241minus3253 DOI 101007s10706-019-00839-8
[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A
comparative evaluation of stress-strain and acoustic emission
methods for quantitative damage assessments of brittle rock
[J] Rock Mechanics and Rock Engineering 2015 48(2)
495minus508 DOI 101007s00603-014-0590-0
[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan
LI Xiang-dong Effects of temperature and age on physico-
mechanical properties of cemented gravel sand backfills [J]
Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6
[33] BARTON N A review of mechanical over-closure and
thermal over-closure of rock joints Potential consequences
for coupled modelling of nuclear waste disposal and
geothermal energy development [J] Tunnelling and
Underground Space Technology 2020 99 103379 DOI
101016jtust2020103379
[34] BAREITHER C A BENSON C H EDIL T B Comparison
of shear strength of sand backfills measured in small-scale
and large-scale direct shear tests [J] Canadian Geotechnical
Journal 2008 45(9) 1224minus1236 DOI 101139t08-058
[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct
shear testing of a marginal material using a large shear box
[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI
101520gtj101237
[36] LI Li Generalized solution for mining backfill design [J]
International Journal of Geomechanics 2014 14(3)
04014006 DOI 101061(asce)gm1943-56220000329
[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of
temperature on compressive strength microstructure
properties and failure pattern of fiber-reinforced cemented
tailings backfill [J] Construction and Building Materials
2019 222 776minus785 DOI 101016jconbuildmat2019 06203
[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of
temperature on the strength development of the tailing-waste
rock backfill of a gold mine [J] Advances in Civil
Engineering 2019 2019 1minus9 DOI 10115520194379606
[39] BERNIER R L LI M G MOERMAN A Effects of tailings
and binder geochemistry on the physical strength of paste
backfill [C] Proceeding of Sudburry99 Sudbury Canada
1999 1113minus1122
[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo
GUO Li-jie SONG K I Experimental investigation on the
relationship between pore characteristics and unconfined
compressive strength of cemented paste backfill [J]
Construction and Building Materials 2018 179 254minus264
DOI 101016jconbuildmat201805224
[41] LI Wen-chen FALL M Sulphate effect on the early age
strength and self-desiccation of cemented paste backfill [J]
Construction and Building Materials 2016 106 296 minus 304
DOI 101016jconbuildmat201512124
[42] SHANG J ZHAO Z MA S On the shear failure of incipient
3188
J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189
J Cent South Univ (2021) 28 3173-3189
rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012
[43] THIRUKUMARAN S INDRARATNA B A review of shear
strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006
(Edited by FANG Jing-hua)
不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应
摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不
同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对
不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性
能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形
较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以
是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切
性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主
应力方向密切相关
关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量
中文导读中文导读
3189