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Transcript of Bill BAMFORD - ats2017.com.auats2017.com.au/wp-content/uploads/2017/11/TUESDAY-LEVEL-5-1210...Shield...
Bill BAMFORD
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INTRODUCTION
PREDICTING TOOL WEAR AND REPLACEMENT RATES FOR MACHINE TUNNELLING1. Tests can be performed on solid rock
substance samples, for rock TBMs2. Tests can be performed on naturally
granular materials, for soft-ground TBMs (e.g. EPB machines, Slurry Shields)
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EXAMPLE : “TOTAL HARDNESS” METHOD
“Total Hardness”
is calculated from
Schmidt Rebound
Hammer Hardness
+
Taber Abraser Test
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EXAMPLE : SINTEF METHOD
CUTTER LIFE INDEX (CLI)
is calculated from
Sievers J-value
Drillability test
+
Abrasion Value Steel
(AVS) test.
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The Norwegian Abrasion Test :Norwegian Abrasion Value (NAV) : Tungsten Carbide Workpiece :
Percussive DrillingAbrasion Value Steel (AVS) :
Steel Workpiece : Hard-Rock TBMs
Soil Abrasion Test (SAT) : Steel Workpiece :
Soft-Ground TBMs
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SAT RESULTS (1)
• Prediction of soft-ground
tunnelling tool life from
lab SAT results;
• NB : lab testing is
conducted on dry
sand and sandy silt
materials.
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SAT RESULTS (2)
• Separate correlations,
for Slurry Shields
&
EPBMs
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•While the SAT (Soil Abrasion Test) is popular, and is being widely used, its fundamental weakness is that it is conducted on dry sandy materials, not widely representative of what most Slurry Shield and EPBM tunnelling operations are conducted in.
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SGAT
• The Soft Ground Abrasion Tester (SGAT) was recently designed and built at the NTNU in Trondheim, Norway.
• With the permission and assistance of its original designer, a second version has been built in Melbourne.
• It enables the abrasiveness of sandy materials to be measured, not in the dry, freely-flowing state, as per the SAT, but rather in the compacted and wet conditions in which they will be penetrated by TBMs.
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HOWEVER ….
• The required sample size to perform SAT is only a few kilograms;
• The required sample size to perform SGAT is a few tens of kilograms.
So, during exploration for a tunnelling project it may be difficult to obtain sufficient masses of material from the exploratory boreholes for significant SGAT testing to be performed.
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UNIVERSITY OF MELBOURNE RESEARCH
1. Investigate correlations between SAT & SGAT values, in comparable materials.
2. Investigate whether blending of different commercially-available sands can allow large quantities of a “synthetic” soil to be assembled in the lab, which will reliably mimic the properties of any natural sand or soil which has been supplied to the lab in small quantities.
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MATERIALS: Commercial Sands
Soil ID Specific Gravity Coefficient of Uniformity Coefficient of Curvature
BTS 2.62 2.23 0.83
MTS 2.60 1.50 0.86
WGS 2.69 5.71 1.19
Brown Turf Sand
(BTS)White Granitic Sand
(WGS)
Muckadilla Turf Sand
(MTS)
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MATERIALS: Naturally Occurring Soils
Soil ID Description Specific Gravity
F Sandy soil (Perth, AU) 2.58
M Mixture of clay, silt & sand (Melbourne, AU) 2.62
W Mixture of clay, silt and sand (Auckland, NZ) 2.64
Soil F Soil WSoil M
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BRTS NTNU MACHINE
SAT Test Piece
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BRTS SGAT MACHINE
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SAMPLE PREPARATION
Proctor
Hammer
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RESULTS & ANALYSIS- Results Comparison
SAT on “M” is not achievable, while SGAT on “M” is the greatest!SAT does not properly simulate field conditions (Density, Moisture content, etc.)
13.3 6.0 13.0 5.6 0 1.2
33.5 40.456.1
19.5
374.1
149.0
0
50
100
150
200
250
300
350
400
BTS MTS WGS F M W
We
igh
t L
oss (
mg
)
SAT
SGAT
NA
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RESULTS & ANALYSIS- Commercial Sands
0
20
40
60
80
100
0 2 4 6 8 10 12 14
SG
AT
Va
lue
(m
g)
Moisture Content (%)
WGS
MTS
BTS
1600
1700
1800
1900
2000
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
Dry
De
ns
ity
(k
g/m
3)
Moisture Content (%)
WGS
MTS
BTS
Compaction SGAT
Maximum abrasivity is not necessarily at the driest or densest condition
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RESULTS & ANALYSIS- Naturally Occurring Soils
Compaction SGAT
Changes in density and moisture condition didn’t affect SGAT value of “F"
1500
1600
1700
1800
1900
2000
0 5 10 15 20
Dry
De
ns
ity
(k
g/m
3)
Moisture Content (%)
F
W
M
0
200
400
600
800
0 5 10 15 20
SG
AT
Va
lue
(m
g)
Moisture Content (%)
W
M
F
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RESULTS & ANALYSIS- Basis for Classification
VL: Very Low Abrasivity
L: Low Abrasivity
M: Medium Abrasivity
H: High Abrasivity
V: Very High Abrasivity
More test data
is required… 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 20 40 60 80 100 120 140 160 180 200
SGAT (mg)
V
L
M
H
VH
22 43 76 147
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RESULTS & ANALYSIS- SGAT vs SAT Test Results
Soil ID Moisture content (%) Abrasivity (SGAT) Abrasivity (SAT)
WGS
2.3 Low
Medium
5.4 Medium
7.5 High
8.5 Medium
12.2 Very Low
M
4.8 Very High
NA
8.2 Very High
11.6 Very High
14.7 Very High
17.7 High
Unlike SAT, for a soft ground soil type, SGAT provides a range of abrasivity values.
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CONCLUSIONS
• Advantage: Improves the accuracy of characterizing ground conditions for soft-ground machine tunnelling
• Advantage: The ability of the SGAT to more accurately and quantitatively measure the abrasiveness of sedimentary deposits and soils, in conditions closely simulating the conditions of density and moisture content in which they will be excavated by a TBM, makes it potentially a far superior tool.
• The widely accepted SAT (Soil Abrasion Test) may continue to be used for broad classification purposes, if sample quantities and testing budgets are limited.
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FUTURE PLAN
•After characterizing the PSD and the soil mineralogy of the small submitted samples, it may be possible by mixing calculated proportions of the several “commercial” sands to construct analogue materials in masses large enough for significant testing at many densities and moisture contents, to bracket the full range of expected variability in-situ.
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FUTURE PLAN
• Planned work at BRTS will enable the injection of different conditioning agents into the test chamber, to quantify the reductions in abrasiveness that may be achieved by appropriate soil conditioning.
• The consequent changes in torque/thrust and power will also show how optimum TBM operating parameters for a particular soil might result from the appropriate soil conditioning agents.
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Typical EPBM in section, showing where conditioning agents may be introduced
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Thank you
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