Research Article Evaluation of an Improved Technique for...

Research ArticleEvaluation of an Improved Technique forGeosynthetic-Reinforced and Pile-Supported Embankment

Jun Zhang12 Shao-wen Liu1 and He-fu Pu3

1Key Laboratory of Highway Construction and Maintenance Technology in Loess RegionShanxi Transportation Research Institute Taiyuan 030006 China2Key Laboratory of Transportation Tunnel Engineering Ministry of Education Chengdu 610031 China3Department of Civil Architectural and Environmental Engineering Missouri University of Science and TechnologyRolla MO 65409 USA

Correspondence should be addressed to Jun Zhang zhangjun hustqqcom

Received 1 May 2015 Revised 27 June 2015 Accepted 28 June 2015

Academic Editor Joao M P Q Delgado

Copyright copy 2015 Jun Zhang et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

With a large number of applications of conventional technique for geosynthetic-reinforced and pile-supported (GRPS)embankment (called CT embankment) many deficiencies have been exposed In view of the deficiencies an improved techniquefixed-geosynthetic-reinforced and pile-supported embankment (called FGT embankment) is developed To investigate theperformance of the FGT embankment the comparison analyses and parametric studies are conducted by Finite Element Method(FEM)The influencing factors investigated include elasticmodulus of soil tensile stiffness of geosynthetics pile length pile spacingand pile elastic modulus In addition the cost evaluation for the FGT embankment and CT embankment is also made The resultsshow that the FGT embankment can significantly reduce the settlement and differential settlement enhance the stability andprovide an economical and effective measure for the construction of high embankment at the bridge approach

1 Introduction

With a large number of applications of conventionaltechnique for geosynthetic-reinforced and pile-supported(GRPS) embankment (called CT embankment) many defi-ciencies have been exposed [1ndash3] For example the efficacyof controlling the settlement and differential settlement isinsufficient and the efficiency of geosynthetics may not befully mobilized The differential settlement in particular isstill great when using the CT embankment at the bridgeapproach This differential settlement could be attributed tothe stiffness difference between the bridge abutment andbridge approach embankment [4ndash6] A small differentialsettlement can produce a significant vehicle bump at the endof the bridge and this vehicle bump can lead to higher vehicleor bridge maintenance costs and discomfort to drivers andpassengers [7 8]

In view of these deficiencies an improved techniquefixed-geosynthetic-reinforced and pile-supported embank-ment (called FGT embankment) is developed and intro-duced herein The structures for the CT and FGT embank-ments are presented in Figure 1 In the FGT embankmentthe geosynthetic is fixed on the pile caps and this fixedsystem is comprised of a steel bar fulcrum and concrete fixedtop In comparison with the CT embankment the numericalanalysis and cost evaluation are carried out to investigate theperformance of FGT embankment in this study

2 Numerical Analysis

21 Numerical Modeling The following studies are onthe basis of a bridge approach in Chang-An Expressway(Figure 2) which is located at the east of MCK + 826 number0 Bridge in Changzhi City central region of China Taking

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015 Article ID 612760 9 pageshttpdxdoiorg1011552015612760

2 Advances in Materials Science and Engineering

Table 1 Material parameters used in the numerical simulations

Material 119864(MPa) 120574(kNm3) 119888(kPa) 120593(∘) ] 119877inter 119867119871(m)Embankment fill 200 190 168 246 030 050 50Silty clay 52 172 142 183 033 065 35Silty soil 76 178 76 197 033 065 60Gravelly sand 300 201 0 286 030 065 40Clay 221 183 157 210 030 080 65Note 119864 is elastic modulus 120574 is unit weight ] is Poissonrsquos ratio 119888 is cohesive strength 120593 is friction angle H is height of embankment fill and L is thickness ofsoil layers

Cushion Geosynthetic

PilePile

Pile cap Steel bar mesh

Soft soil

(a) CT structure

PilePile

Steel mesh

Concrete fixed top

Pile cap

GeosyntheticSteel bar fulcrum

Soft soil

(b) FGT structure

Figure 1 Illustration of CT and FGT structures [3]

Pier

GeosyntheticConcrete fixed top

Figure 2 Bridge approach at MCK + 826 number 0 Bridge

this project as a prototype a two-dimensional finite elementmodel is established using the software package PLAXIS Dueto symmetry of the embankment half of the embankmentcross section is modeled in PLAXIS The parameters valuesused in the numerical simulations shown in Table 1 areobtained from the in situ and laboratory tests To convertthe three-dimensional problem into a two-dimensional onethe equivalent elastic modulus of pile in the two-dimensional

A Silty clay

Silty soil

Gravelly sand

Hard clay

Piles

GeosyntheticTraffic load

FGT structure CT structureEmbankment fillBC

170m 75m 355m

50

m200

m

025

m

s = 35m

L = 35m

L = 60m

L = 40m

L = 65m

Figure 3 Dimensions and boundary conditions in numericalmodel

model is calculated as119864eq = 119864119901119898+119864119904(1minus119898) where119864119901 and119864119904are the elastic modulus of the pile and the soil respectivelyand 119898 is the area replacement ratio [9] The geometry andboundary conditions of the model are the same as thosepresented by Zhang et al [3]

The dimensions and the boundary conditions in thenumerical model are presented in Figure 3 The boundarycondition at the bottom is assumed to be completely rigidand the vertical boundaries are fixed against horizontaldisplacement but allowed to move in the vertical directionThe subgrade and embankment fill are modeled as linearlyelastic-plastic materials with Mohr-Coulomb failure crite-rion The piles and geosynthetic are modeled as linearlyelastic materials

In the numerical modeling the 15-node triangular ele-ments (Figure 4(a)) are used to model soil layers andembankment fill The 15-node triangle is the most accurateelement in the PLAXIS and can provide a high accuracyresults for complex problems The 5-node beam (geogrid)elements (Figure 4(b)) and five pairs of interface elements(Figure 4(c)) are used together with 15-node triangular ele-ments The soil-structure interface is modeled as elastic-plastic In elastic region the shear stress at the interface isgiven by

|120591| lt 120590119899tan1205931015840 + 1198881015840 (1)

In plastic region the shear stress at the interface is given by

|120591| = 120590119899tan1205931015840 + 1198881015840 (2)

where 120590119899is normal stress and 1205931015840 and 1198881015840 are friction angle

and cohesive strength of the subgrade-structure interface

Advances in Materials Science and Engineering 3

(a) 15-node triangular elements

(b) 5-node beam (geogrid) elements

(c) Five pairs of interface elements

Figure 4 Basic elements used in the numerical model

respectively The strength properties of interfaces can bedetermined from the subgrade (embankment) propertieswith a correlated strength reduction factor 119877inter and arecalculated as

tan1205931015840 = 119877inter tan120593soil

1198881015840

= 119877inter119888soil(3)

where 120593soil and 119888soil are friction angle and cohesive strength ofthe subgrade soil [10]

22 Model Calibration A model calibration was conductedto ensure that the numerical modeling is reasonable andrepresentative of the field conditions [3] The settlementsat the centerline of the ground surface (Point A as shownin Figure 3) and lateral displacements at 10m away fromthe embankment toe (Point B as shown in Figure 3) in theCT and FGT cases are measured by the settlement gaugesand total station instrument respectively Figure 5 shows thatthe simulation results exhibit a reasonable agreement withthe field measurement data The pile efficacy which is theratio of the embankment load on a single pile to the totalembankment load over the tributary area of the pile below thegeosynthetic changedwith the embankment height as shownin Figure 6 The calculated results are again shown to be in

good agreement with field measured data The above modelcalibration forms the basis for the following study

23 Results and Comparisons The settlement profiles atembankment crest for both cases are presented in Figure 7The settlement profile for the FGT embankment is similarto that for the CT embankment However the settlementfor the FGT embankment is much smaller than that forthe CT embankment The maximum settlement for the FGTembankment and CT embankment is 751mm and 835mmrespectively

Stability is one of the most important issues for highembankment [11ndash13] As an important control parameter forthe stability of high embankment [14] the lateral displace-ment is discussed herein Figure 8 shows that the lateraldisplacement at the embankment toe varies with depthAs expected the lateral displacement for the CT embank-ment is greater than that for the FGT embankment Themaximum lateral displacements for the FGT embankmentand CT embankment are 186 and 229mm respectivelyThe maximum lateral displacement for the FGT embank-ment is reduced by 188 as compared to that for the CTembankmentTheFGT embankment can significantly reducethe lateral displacement and thus improve the embankmentstability

Figure 9 shows that the vertical displacements of geosyn-thetic display different responses for both cases The verticaldisplacement for the CT embankment is shown to be largerthan that for the FGT embankment However the differentialvertical displacements between the valley and adjacent heavefor the FGT embankment are much larger than those forthe CT embankment Below the embankment crest themaximum differential vertical displacement for the FGTembankment is 321mm and is more than 3 times larger thanthat for the CT embankment

The maximum tension of geosynthetic is an importantindex for evaluating the efficiency of geosynthetic [15] Asshown in Figure 10 the maximum tension in both casesincreases with increasing embankment height For all theembankment heights the maximum tension for the FGTembankment is greater than that for the CT embankmentIn addition the difference of the maximum tension betweenthe two cases tends to increase with increasing embankmentheight Thus the FGT embankment can better mobilizethe geosynthetic efficiency for all the embankment heightconsidered

The distributions of lateral displacement at the top ofthe piles for both cases are presented in Figure 11 Thelateral displacements for both cases generally increase withthe distance from the embankment centerline The lateraldisplacement curve for the FGT embankment is smootherthan that for the CT embankment It can be concluded thatthe FGT embankment can reduce the lateral displacement atthe top of the piles and improve the interaction between thepiles

The variation of maximum bending moment of pileswith distance from embankment centerline is presented inFigure 12 In general the maximum bending moments forthe FGT embankment are greater than those for the CT


0

20

40

60

80

10 20 30 40 50

FGT (calculated) CT (calculated)CT (measured)

Embankment height (m)

FGT (measured)

Settl

emen

t (m

m)

(a) Settlement at centerline of ground surface

FGT (calculated) CT (calculated)CT (measured)FGT (measured)

0

5

10

15

20

10 20 30 40 50Embankment height (m)

Late

ral d

ispla

cem

ent (

mm

)

(b) Lateral displacement at 10m away from embankment toe

Figure 5 Comparisons of numerical results with field measurements

0

20

40

60

80

100


Pile

effica

cy (

)


Figure 6 Variation of pile efficacy below geosynthetic with emban-kment height

50

60

70

80

90

1000 3 6 9 12 15

FGTCT

Settl

emen

t (m

m)

18Distance from center of embankment (m)

Figure 7 Settlement at embankment crest

15

12

9

6

3

0

0 5 10 15 20 25

FGTCT

Lateral displacement (mm)

Dep

th (m

)

Figure 8 Variation of lateral displacement with depth

0 5 10 15 20 2580

60

40

20

0

Vert

ical

disp

lace

men

t (m

m)

Distance from center of embankment (m)

FGTCT

Figure 9 Vertical displacement of geosynthetic


0

10

20

30

40

50

00 10 20 30 40 50Embankment height (m)

Max

imum

tens

ion

(kN

m)

FGTCT

Figure 10 Variation of maximum tension of geosynthetic withembankment height

0

6

12

18

5 10 15 20

24

30

0 25Distance from center of embankment (m)

Late

ral d

ispla

cem

ent (

mm

)

FGTCT

Figure 11 Variation of lateral displacement at pile top with distancefrom embankment centerline

embankment In addition the distribution of maximumbending moment for the FGT embankment is more uniformrelative to the CT embankment The maximum bendingmoment among the piles for the CT embankment is 13 timesthat for the FGT embankment The FGT embankment isshown to improve the interaction between the piles

24 Influencing Factors To further investigate the perfor-mance of the FGT embankment five key influencing factorsare selected for parametric study The influencing factorsinclude elastic modulus of soil tensile stiffness of geosyn-thetic pile length pile spacing and pile elastic modulusIn the parametric study the FGT embankment and CTembankment mentioned above are the two baseline casesThe maximum settlement at the embankment crest the lat-eral displacement at the embankment toe and the maximumtension of geosynthetic are investigated

The influence of elastic modulus of soil is studied byanalyzing four cases with 06 08 10 and 12 times ofthe elastic modulus of soil (including all soil layers) for

0

5

10

15

20

175 525 875 1225 1575 1925

FGTCT


Max

imum

mom

ent (

kNmiddotm

)

Figure 12 Variation of maximum bending moment of piles withdistance from embankment centerline

the baseline cases As shown in Figure 13(a) the maximumsettlement and lateral displacement decrease with increasingelastic modulus of soil At a low elastic modulus (06 timesof the elastic modulus of soil) the maximum settlementand lateral displacement for the FGT embankment are muchsmaller than those for the CT embankment For the FGTembankment the maximum settlement and lateral displace-ment are reduced by 191 and 101 as compared to the CTembankment respectively The differences of the maximumsettlement and lateral displacement between the two casesdecrease gradually with increasing elastic modulus of soilThe effect of elastic modulus of soil on the maximum tensionof geosynthetic is presented in Figure 13(b) The maximumtension decreases with increasing elastic modulus of soilfor the FGT embankment However the elastic modulus ofsoil has only slight influence on the maximum tension forthe CT embankment Thus the FGT embankment is morecompetent for a soft soil condition

Geosynthetic used for theGRPS embankment is expectedto improve the pile efficiency and embankment stabilityby transferring load from the subgrade to the piles andreducing lateral displacement [16] The influence of tensilestiffness of geosynthetic is studied by analyzing four caseswith tensile stiffness of geosynthetic = 100 1000 10000 and100000 kNm Figure 14(a) shows that the tensile stiffnessof geosynthetic has a limited influence on the maximumsettlement for both cases However the lateral displace-ment is reduced significantly with increasing tensile stiffnessof geosynthetic At the tensile stiffness of geosynthetic of100 kNm the lateral displacement for the FGT embankmentis reduced by 161 as compared to the lateral displace-ment for CT embankment and the corresponding reductionincreases to 342 at the tensile stiffness of geosynthetic of100000 kNm As shown in Figure 14(b) the maximum ten-sion increaseswith increasing tensile stiffness of geosyntheticThe maximum tension for the FGT embankment is greaterthan that for the CT embankment In addition the differenceof the maximum tension between the two cases tends to begreater with increasing tensile stiffness of geosynthetic


Late

ral d

ispla

cem

ent

at em

bank

men

t toe

(mm

)

10

20

30

40M

axim

um se

ttlem

ent (

mm

)

0

50

50

70

90

110

130

150

06 08 10 12Influential coefficient (n)

Maximum settlement-FGTMaximum settlement-CT

Lateral displacement-FGTLateral displacement-CT

(a) Maximum settlement and lateral displacement

0

12

24

36

48

60


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension

Figure 13 Influence coefficient of elastic modulus of soil

0

20

40

60

80

100

at em

bank

men

t toe

(mm

)

0

5

10

15

20

25

100 1000 10000 100000

Max

imum

settl

emen

t (m

m)

Late

ral d

ispla

cem

ent

Tensile stiffness (kNm)




120

150

0

30

60

90

100 1000 10000 100000Tensile stiffness (kNm)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension

Figure 14 Influence of geosynthetic tensile stiffness

The influence of pile length is studied by analyzingfour cases with pile length of 60 80 100 and 120mAs shown in Figure 15(a) the maximum settlement andlateral displacement change with the pile length for bothcases As the pile length increases from 60 to 120m themaximum settlement decreases only slightly at first but hasa jump when the pile length increases from 80 to 100mThen the influence of pile length becomes less importantagain when the pile length exceeds 100m Similarly thedegree of decrease on the lateral displacement becomesmuchsharper with the pile length increase from 80 to 100m Thisphenomenon occurs because the piles are penetrated intofirm soil layer Figure 15(b) shows that the pile length has asignificant influence on the maximum tension for the FGTembankment but limited influence for the CT embankment

Pile spacing is an important design parameter for GRPSembankment Closely spaced piles can transfer the surchargeload easily but are much uneconomical A wide pile spacinghowever is likely to cause bearing capacity failure or slopestability failure [17] In this study the influence of pilespacing is studied by analyzing four cases with pile spacingof 25 30 35 and 40m The maximum settlement and

lateral displacement increase with increasing pile spacing aspresented in Figure 16(a) For both the FGT embankmentand CT embankment the maximum settlement and lateraldisplacement increase with increasing pile spacing As shownin Figure 16(b) the maximum tension of geosynthetic for theFGT embankment firstly decreases and then increases withincreasing pile spacing In contrast the maximum tensionfor the CT embankment firstly increases and then decreasesOverall the effect of pile spacing on themaximum tension forthe CT embankment is less important than that for the FGTembankment

The influence of pile elastic modulus is studied by analyz-ing four cases with pile elastic modulus of 05 10 50 and100MPa As shown in Figure 17(a) the pile elastic modulushas a limited influence on the maximum settlement andlateral displacement for both cases Similarly Figure 17(b)shows that the maximum tensions of geosynthetic remainnearly constant with the increase of pile elastic modulus

25 Discussion The influence of a factor on the maximumsettlement at the embankment crest the lateral displacement


at em

bank

men

t toe

(mm

)

50

70

90

110

130

150

60 80 100 1200

10

20

30

40

50M

axim

um se

ttlem

ent (

mm

)

Late

ral d

ispla

cem

ent

Pile length (m)




0

10

20

30

40

50

60 80 100 120Pile length (m)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension

Figure 15 Influence of pile length

Late

ral d

ispla

cem

ent

50

60

70

80

90

100

25 30 35 400

5

10

15

20

25

Max

imum

settl

emen

t (m

m)

at em

bank

men

t toe

(mm

)

Pile spacing (m)




0

10

20

30

40

50

25 30 35 40Pile spacing (m)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension

Figure 16 Influence of pile spacing

at the embankment toe and themaximum tension of geosyn-thetic is considered positive or negative based on its effecton the performance of FGT embankment The positive andnegative effects are defined as the decrease and increase ofthe performance of FGT embankment with an increase ofthe value of the factor respectively The degree of influenceof the factor is defined as the change of the values relative tothe mean values [18] For example the maximum settlementsfor the pile length of 60 80 100 and 120m are 109 9475 and 67mm respectively Thus the degree of influence ofthe pile length on the maximum settlement is calculated as(109 minus 67)[(109 + 67)2] = 48 The degree of influence isdivided into three grades high (greater than 60) medium(between 30 and 60) and low (less than 30) Thedetailed calculation method and the grade of the influencedegree can be found in Huang and Han [18] The degrees ofinfluence for each factor are listed in Table 2 The grades ofthe influence degree for each factor are presented in Table 3

In this study Tables 2 and 3 show that the pile length pilespacing and pile elastic modulus have a limited influence onthe performance of FGT embankment The elastic modulusof soil and tensile stiffness of geosynthetic have significant

Table 2 The degree of influence ()

Factors 119864 119864119892

119871119901

119863 119864119901

Smax 55 7 48 10 5Ltoe 65 73 5 8 1Tmax 37 177 24 46 3Note Smax is maximum settlement at embankment crest Ltoe is lateraldisplacement at embankment toe Tmax is maximum tension 119864

119892is tensile

stiffness of geosynthetic 119871119901is pile length 119864

119901is elastic modulus of pile D is

pile spacing

Table 3 The grades of influence degree

Factors 119864 119864119892

119871119901

119863 119864119901

Smax Medium (+) Low (+) Medium (+) Low (minus) Low (+)Ltoe High (+) High (+) Low (minus) Low (minus) Low (minus)Tmax Medium (+) High (minus) Low (minus) Medium (minus) Low (minus)

influence and are the two important factors for the perfor-mance of FGT embankment


Pile elastic modulus (GPa)

0

10

20

30

40

at em

bank

men

t toe

(mm

)

0

20

40

60

80

100M

axim

um se

ttlem

ent (

mm

)

05 10 50 100

50

Late

ral d

ispla

cem

ent




0

20

40

60

80

100

Max

imum

tens

ion

(kN

m)

05 10 50 100Pile elastic modulus (GPa)

FGTCT

(b) Maximum tension

Figure 17 Influence of pile elastic modulus

Table 4 Cost evaluation for CT and FGT embankments (RMB 1000Yuan)

Labor cost Material cost Machinery cost Total costCT 21206 21272 20117 62595FGT 21388 22710 20128 64226Incremental cost 182 1433 11 1631Incremental rate 09 68 01 26

3 Cost Evaluation

In this study the costs of ground improvement for theFGT embankment and CT embankment in the trial bridgeapproach embankment are comparedThe costs include thosefor labor materials and machinery The cost evaluation forthe baseline case with embankment length of 10 km for theCT and FGT embankments is calculated and presented inTable 4

For the FGT embankment the total cost is increasedby only 26 relative to the CT embankment Howeverthe maximum settlement at the embankment crest and thelateral displacement at the embankment toe for the FGTembankment are decreased by 101 and 188 respectivelyrelative to the CT embankment as shown in Figures 7 and 8Take the pile length and pile spacing for example the changerates of the cost and efficiency are presented in Table 5 Theinfluence on the maximum settlement lateral displacementand maximum tension is considered positive or negativebased on its effect on the performance of embankment asmentioned aboveThe FGT embankment is shown to providean economical and effective measure for the construction ofhigh embankment at the bridge approach

4 Conclusions

In this paper to improve the performance of the CT embank-ment at the bridge approach the FGT embankment is pro-

Table 5 Change rates of the cost and efficiency

FGT Pile length-CT Pile spacing-CTBaseline case(m) mdash 100 35Change case(m) mdash 120 30Total cost 26 189 140Maximum settlement 101 97 76Lateral displacement 188 minus05 08Maximum tension minus1784 minus08 minus138

posed and studied The numerical analysis and cost evalu-ation are conducted to investigate the performance of FGTembankment From this study the following conclusions canbe drawn

(1) The FGT embankment can significantly reduce thesettlement and lateral displacement and improve loadtransfer from the subgrade to piles

(2) The FGT embankment can significantly improve theembankment stability and the geosynthetic efficiency

(3) In the FGT embankment the average values ofthe maximum bending moment in the piles aregreater than those in the CT embankment Howeverthe maximum bending moment among the piles issmaller than that in the CT embankment in this study

(4) The pile length pile spacing and pile elastic modulusare shown to have limited influence on the perfor-mance of FGT embankment The elastic modulusof soil and tensile stiffness of geosynthetic havesignificant influence on the performance of FGTembankment

(5) The performance of the FGT embankment is im-proved significantly with only a slight increase of thetotal cost Thus the FGT embankment can providean economical and effectivemeasure for the construc-tion of high embankment at the bridge approach


Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (NSFC) (Grant no 51278216) theBasic Research Program in Shanxi Province (Grant no2014021033-1) and the Research Fund of Key Laboratory ofTransportation Tunnel Engineering Ministry of Education(Grant no TTE2014-05) The authors would like to expresstheir gratitude for the financial support

References

[1] G S Liu L W Kong and X W Li ldquoAnalysis of treatmentscheme for soft foundation on in expressway widening projectand its verificationrdquo Chinese Journal of Rock Mechanics andEngineering vol 27 no 2 pp 309ndash315 2008 (Chinese)

[2] K Fei and H-L Liu ldquoField test study and numerical analysisof a geogrid-reinforced and pile-supported embankmentrdquo Rockand SoilMechanics vol 30 no 4 pp 1004ndash1011 2009 (Chinese)

[3] J Zhang J J Zheng and Y E Lu ldquoEvaluation of the new tech-nique of geogrid-reinforced and pile-supported embankment atbridge approachrdquo Journal of Bridge Engineering vol 19 no 4Article ID 06014001 2014

[4] R M Bakeer M A Shutt J Q Zhong S C Das andM Morvant ldquoPerformance of pile-supported bridge approachslabsrdquo Journal of Bridge Engineering vol 10 no 2 pp 228ndash2372005

[5] D Q Li and D Davis ldquoTransition of railroad bridge app-roachesrdquo Journal of Geotechnical and Geoenvironmental Engi-neering vol 131 no 11 pp 1392ndash1398 2005

[6] S Roy and G Thiagarajan ldquoNonlinear finite-element analysisof reinforced concrete bridge approach slabrdquo Journal of BridgeEngineering vol 12 no 6 pp 801ndash806 2007

[7] D J White M M Mekkawy S Sritharan and M T SuleimanldquolsquoUnderlyingrsquo causes for settlement of bridge approach pave-ment systemsrdquo Journal of Performance of Constructed Facilitiesvol 21 no 4 pp 273ndash282 2007

[8] H-L Zhang and C-S Hu ldquoDetermination of allowable differ-ential settlement in bridge approach due to vehicle vibrationsrdquoJournal of Bridge Engineering vol 12 no 2 pp 154ndash163 2007

[9] J Huang J Han and S Oztoprak ldquoCoupled mechanicaland hydraulic modeling of geosynthetic-reinforced column-supported embankmentsrdquo Journal of Geotechnical and Geoen-vironmental Engineering vol 135 no 8 pp 1011ndash1021 2009

[10] PLAXIS 2D V8 Reference manual 2002[11] M De Souza Soares De Almeida M Ehrlich A P Spotti

and M E S Maroues ldquoEmbankment supported on piles withbiaxial geogridsrdquoProceedings of the Institution of Civil EngineersGeotechnical Engineering vol 160 no 4 pp 185ndash192 2007

[12] S W Abusharar and J Han ldquoTwo-dimensional deep-seatedslope stability analysis of embankments over stone columns-improved soft clayrdquo Engineering Geology vol 120 no 1ndash4 pp103ndash110 2011

[13] T Eskisar J Otani and J Hironaka ldquoVisualization of soilarching on reinforced embankment with rigid pile foundation

using X-ray CTrdquoGeotextiles andGeomembranes vol 32 pp 44ndash54 2012

[14] S Murugesan and K Rajagopal ldquoShear load tests on stonecolumns with and without geosynthetic encasementrdquo Geotech-nical Testing Journal vol 32 no 1 pp 76ndash85 2009

[15] J Han and M A Gabr ldquoNumerical analysis of geosynthetic-reinforced and pile-supported earth platforms over soft soilrdquoJournal of Geotechnical and Geoenvironmental Engineering vol128 no 1 pp 44ndash53 2002

[16] YM ChenW P Cao and R P Chen ldquoAn experimental investi-gation of soil arching within basal reinforced and unreinforcedpiled embankmentsrdquo Geotextiles and Geomembranes vol 26no 2 pp 164ndash174 2008

[17] J Huang Coupled mechanical and hydraulic modeling ofgeosynthetic-reinforced column-supported embankments [PhDthesis] University of Kansas Lawrence Kan USA 2007

[18] J Huang and J Han ldquoTwo-dimensional parametric study ofgeosynthetic-reinforced column-supported embankments bycoupled hydraulic and mechanical modelingrdquo Computers andGeotechnics vol 37 no 5 pp 638ndash648 2010

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Table 1 Material parameters used in the numerical simulations

Material 119864(MPa) 120574(kNm3) 119888(kPa) 120593(∘) ] 119877inter 119867119871(m)Embankment fill 200 190 168 246 030 050 50Silty clay 52 172 142 183 033 065 35Silty soil 76 178 76 197 033 065 60Gravelly sand 300 201 0 286 030 065 40Clay 221 183 157 210 030 080 65Note 119864 is elastic modulus 120574 is unit weight ] is Poissonrsquos ratio 119888 is cohesive strength 120593 is friction angle H is height of embankment fill and L is thickness ofsoil layers

Cushion Geosynthetic

PilePile

Pile cap Steel bar mesh

Soft soil

(a) CT structure

PilePile

Steel mesh

Concrete fixed top

Pile cap

GeosyntheticSteel bar fulcrum

Soft soil

(b) FGT structure

Figure 1 Illustration of CT and FGT structures [3]

Pier

GeosyntheticConcrete fixed top

Figure 2 Bridge approach at MCK + 826 number 0 Bridge

this project as a prototype a two-dimensional finite elementmodel is established using the software package PLAXIS Dueto symmetry of the embankment half of the embankmentcross section is modeled in PLAXIS The parameters valuesused in the numerical simulations shown in Table 1 areobtained from the in situ and laboratory tests To convertthe three-dimensional problem into a two-dimensional onethe equivalent elastic modulus of pile in the two-dimensional

A Silty clay

Silty soil

Gravelly sand

Hard clay

Piles

GeosyntheticTraffic load

FGT structure CT structureEmbankment fillBC

170m 75m 355m

50

m200

m

025

m

s = 35m

L = 35m

L = 60m

L = 40m

L = 65m

Figure 3 Dimensions and boundary conditions in numericalmodel

model is calculated as119864eq = 119864119901119898+119864119904(1minus119898) where119864119901 and119864119904are the elastic modulus of the pile and the soil respectivelyand 119898 is the area replacement ratio [9] The geometry andboundary conditions of the model are the same as thosepresented by Zhang et al [3]

The dimensions and the boundary conditions in thenumerical model are presented in Figure 3 The boundarycondition at the bottom is assumed to be completely rigidand the vertical boundaries are fixed against horizontaldisplacement but allowed to move in the vertical directionThe subgrade and embankment fill are modeled as linearlyelastic-plastic materials with Mohr-Coulomb failure crite-rion The piles and geosynthetic are modeled as linearlyelastic materials

In the numerical modeling the 15-node triangular ele-ments (Figure 4(a)) are used to model soil layers andembankment fill The 15-node triangle is the most accurateelement in the PLAXIS and can provide a high accuracyresults for complex problems The 5-node beam (geogrid)elements (Figure 4(b)) and five pairs of interface elements(Figure 4(c)) are used together with 15-node triangular ele-ments The soil-structure interface is modeled as elastic-plastic In elastic region the shear stress at the interface isgiven by

|120591| lt 120590119899tan1205931015840 + 1198881015840 (1)

In plastic region the shear stress at the interface is given by

|120591| = 120590119899tan1205931015840 + 1198881015840 (2)

where 120590119899is normal stress and 1205931015840 and 1198881015840 are friction angle

and cohesive strength of the subgrade-structure interface








1198881015840

= 119877inter119888soil(3)











0

20

40

60

80

10 20 30 40 50



FGT (measured)

Settl

emen

t (m

m)



0

5

10

15

20


Late

ral d

ispla

cem

ent (

mm

)



0

20

40

60

80

100


Pile

effica

cy (

)



50

60

70

80

90

1000 3 6 9 12 15

FGTCT

Settl

emen

t (m

m)



15

12

9

6

3

0

0 5 10 15 20 25

FGTCT


Dep

th (m

)


0 5 10 15 20 2580

60

40

20

0

Vert

ical

disp

lace

men

t (m

m)


FGTCT



0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT


0

6

12

18

5 10 15 20

24

30


Late

ral d

ispla

cem

ent (

mm

)

FGTCT





0

5

10

15

20

175 525 875 1225 1575 1925

FGTCT


Max

imum

mom

ent (

kNmiddotm

)





Late

ral d

ispla

cem

ent

at em

bank

men

t toe

(mm

)

10

20

30

40M

axim

um se

ttlem

ent (

mm

)

0

50

50

70

90

110

130

150





0

12

24

36

48

60


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


0

20

40

60

80

100

at em

bank

men

t toe

(mm

)

0

5

10

15

20

25

100 1000 10000 100000

Max

imum

settl

emen

t (m

m)

Late

ral d

ispla

cem

ent





120

150

0

30

60

90


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension








at em

bank

men

t toe

(mm

)

50

70

90

110

130

150

60 80 100 1200

10

20

30

40

50M

axim

um se

ttlem

ent (

mm

)

Late

ral d

ispla

cem

ent

Pile length (m)




0

10

20

30

40

50

60 80 100 120Pile length (m)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


Late

ral d

ispla

cem

ent

50

60

70

80

90

100

25 30 35 400

5

10

15

20

25

Max

imum

settl

emen

t (m

m)

at em

bank

men

t toe

(mm

)

Pile spacing (m)




0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension





Factors 119864 119864119892

119871119901

119863 119864119901


119892is tensile



pile spacing


Factors 119864 119864119892

119871119901

119863 119864119901





0

10

20

30

40

at em

bank

men

t toe

(mm

)

0

20

40

60

80

100M

axim

um se

ttlem

ent (

mm

)

05 10 50 100

50

Late

ral d

ispla

cem

ent




0

20

40

60

80

100

Max

imum

tens

ion

(kN

m)


FGTCT

(b) Maximum tension




3 Cost Evaluation



4 Conclusions













Acknowledgments


References



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










1198881015840

= 119877inter119888soil(3)











0

20

40

60

80

10 20 30 40 50



FGT (measured)

Settl

emen

t (m

m)



0

5

10

15

20


Late

ral d

ispla

cem

ent (

mm

)



0

20

40

60

80

100


Pile

effica

cy (

)



50

60

70

80

90

1000 3 6 9 12 15

FGTCT

Settl

emen

t (m

m)



15

12

9

6

3

0

0 5 10 15 20 25

FGTCT


Dep

th (m

)


0 5 10 15 20 2580

60

40

20

0

Vert

ical

disp

lace

men

t (m

m)


FGTCT



0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT


0

6

12

18

5 10 15 20

24

30


Late

ral d

ispla

cem

ent (

mm

)

FGTCT





0

5

10

15

20

175 525 875 1225 1575 1925

FGTCT


Max

imum

mom

ent (

kNmiddotm

)





Late

ral d

ispla

cem

ent

at em

bank

men

t toe

(mm

)

10

20

30

40M

axim

um se

ttlem

ent (

mm

)

0

50

50

70

90

110

130

150





0

12

24

36

48

60


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


0

20

40

60

80

100

at em

bank

men

t toe

(mm

)

0

5

10

15

20

25

100 1000 10000 100000

Max

imum

settl

emen

t (m

m)

Late

ral d

ispla

cem

ent





120

150

0

30

60

90


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension








at em

bank

men

t toe

(mm

)

50

70

90

110

130

150

60 80 100 1200

10

20

30

40

50M

axim

um se

ttlem

ent (

mm

)

Late

ral d

ispla

cem

ent

Pile length (m)




0

10

20

30

40

50

60 80 100 120Pile length (m)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


Late

ral d

ispla

cem

ent

50

60

70

80

90

100

25 30 35 400

5

10

15

20

25

Max

imum

settl

emen

t (m

m)

at em

bank

men

t toe

(mm

)

Pile spacing (m)




0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension





Factors 119864 119864119892

119871119901

119863 119864119901


119892is tensile



pile spacing


Factors 119864 119864119892

119871119901

119863 119864119901





0

10

20

30

40

at em

bank

men

t toe

(mm

)

0

20

40

60

80

100M

axim

um se

ttlem

ent (

mm

)

05 10 50 100

50

Late

ral d

ispla

cem

ent




0

20

40

60

80

100

Max

imum

tens

ion

(kN

m)


FGTCT

(b) Maximum tension




3 Cost Evaluation



4 Conclusions













Acknowledgments


References



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

20

40

60

80

10 20 30 40 50



FGT (measured)

Settl

emen

t (m

m)



0

5

10

15

20


Late

ral d

ispla

cem

ent (

mm

)



0

20

40

60

80

100


Pile

effica

cy (

)



50

60

70

80

90

1000 3 6 9 12 15

FGTCT

Settl

emen

t (m

m)



15

12

9

6

3

0

0 5 10 15 20 25

FGTCT


Dep

th (m

)


0 5 10 15 20 2580

60

40

20

0

Vert

ical

disp

lace

men

t (m

m)


FGTCT



0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT


0

6

12

18

5 10 15 20

24

30


Late

ral d

ispla

cem

ent (

mm

)

FGTCT





0

5

10

15

20

175 525 875 1225 1575 1925

FGTCT


Max

imum

mom

ent (

kNmiddotm

)





Late

ral d

ispla

cem

ent

at em

bank

men

t toe

(mm

)

10

20

30

40M

axim

um se

ttlem

ent (

mm

)

0

50

50

70

90

110

130

150





0

12

24

36

48

60


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


0

20

40

60

80

100

at em

bank

men

t toe

(mm

)

0

5

10

15

20

25

100 1000 10000 100000

Max

imum

settl

emen

t (m

m)

Late

ral d

ispla

cem

ent





120

150

0

30

60

90


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension








at em

bank

men

t toe

(mm

)

50

70

90

110

130

150

60 80 100 1200

10

20

30

40

50M

axim

um se

ttlem

ent (

mm

)

Late

ral d

ispla

cem

ent

Pile length (m)




0

10

20

30

40

50

60 80 100 120Pile length (m)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


Late

ral d

ispla

cem

ent

50

60

70

80

90

100

25 30 35 400

5

10

15

20

25

Max

imum

settl

emen

t (m

m)

at em

bank

men

t toe

(mm

)

Pile spacing (m)




0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension





Factors 119864 119864119892

119871119901

119863 119864119901


119892is tensile



pile spacing


Factors 119864 119864119892

119871119901

119863 119864119901





0

10

20

30

40

at em

bank

men

t toe

(mm

)

0

20

40

60

80

100M

axim

um se

ttlem

ent (

mm

)

05 10 50 100

50

Late

ral d

ispla

cem

ent




0

20

40

60

80

100

Max

imum

tens

ion

(kN

m)


FGTCT

(b) Maximum tension




3 Cost Evaluation



4 Conclusions













Acknowledgments


References



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT


0

6

12

18

5 10 15 20

24

30


Late

ral d

ispla

cem

ent (

mm

)

FGTCT





0

5

10

15

20

175 525 875 1225 1575 1925

FGTCT


Max

imum

mom

ent (

kNmiddotm

)





Late

ral d

ispla

cem

ent

at em

bank

men

t toe

(mm

)

10

20

30

40M

axim

um se

ttlem

ent (

mm

)

0

50

50

70

90

110

130

150





0

12

24

36

48

60


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


0

20

40

60

80

100

at em

bank

men

t toe

(mm

)

0

5

10

15

20

25

100 1000 10000 100000

Max

imum

settl

emen

t (m

m)

Late

ral d

ispla

cem

ent





120

150

0

30

60

90


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension








at em

bank

men

t toe

(mm

)

50

70

90

110

130

150

60 80 100 1200

10

20

30

40

50M

axim

um se

ttlem

ent (

mm

)

Late

ral d

ispla

cem

ent

Pile length (m)




0

10

20

30

40

50

60 80 100 120Pile length (m)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


Late

ral d

ispla

cem

ent

50

60

70

80

90

100

25 30 35 400

5

10

15

20

25

Max

imum

settl

emen

t (m

m)

at em

bank

men

t toe

(mm

)

Pile spacing (m)




0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension





Factors 119864 119864119892

119871119901

119863 119864119901


119892is tensile



pile spacing


Factors 119864 119864119892

119871119901

119863 119864119901





0

10

20

30

40

at em

bank

men

t toe

(mm

)

0

20

40

60

80

100M

axim

um se

ttlem

ent (

mm

)

05 10 50 100

50

Late

ral d

ispla

cem

ent




0

20

40

60

80

100

Max

imum

tens

ion

(kN

m)


FGTCT

(b) Maximum tension




3 Cost Evaluation



4 Conclusions













Acknowledgments


References



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Late

ral d

ispla

cem

ent

at em

bank

men

t toe

(mm

)

10

20

30

40M

axim

um se

ttlem

ent (

mm

)

0

50

50

70

90

110

130

150





0

12

24

36

48

60


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


0

20

40

60

80

100

at em

bank

men

t toe

(mm

)

0

5

10

15

20

25

100 1000 10000 100000

Max

imum

settl

emen

t (m

m)

Late

ral d

ispla

cem

ent





120

150

0

30

60

90


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension








at em

bank

men

t toe

(mm

)

50

70

90

110

130

150

60 80 100 1200

10

20

30

40

50M

axim

um se

ttlem

ent (

mm

)

Late

ral d

ispla

cem

ent

Pile length (m)




0

10

20

30

40

50

60 80 100 120Pile length (m)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


Late

ral d

ispla

cem

ent

50

60

70

80

90

100

25 30 35 400

5

10

15

20

25

Max

imum

settl

emen

t (m

m)

at em

bank

men

t toe

(mm

)

Pile spacing (m)




0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension





Factors 119864 119864119892

119871119901

119863 119864119901


119892is tensile



pile spacing


Factors 119864 119864119892

119871119901

119863 119864119901





0

10

20

30

40

at em

bank

men

t toe

(mm

)

0

20

40

60

80

100M

axim

um se

ttlem

ent (

mm

)

05 10 50 100

50

Late

ral d

ispla

cem

ent




0

20

40

60

80

100

Max

imum

tens

ion

(kN

m)


FGTCT

(b) Maximum tension




3 Cost Evaluation



4 Conclusions













Acknowledgments


References



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




at em

bank

men

t toe

(mm

)

50

70

90

110

130

150

60 80 100 1200

10

20

30

40

50M

axim

um se

ttlem

ent (

mm

)

Late

ral d

ispla

cem

ent

Pile length (m)




0

10

20

30

40

50

60 80 100 120Pile length (m)

Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension


Late

ral d

ispla

cem

ent

50

60

70

80

90

100

25 30 35 400

5

10

15

20

25

Max

imum

settl

emen

t (m

m)

at em

bank

men

t toe

(mm

)

Pile spacing (m)




0

10

20

30

40

50


Max

imum

tens

ion

(kN

m)

FGTCT

(b) Maximum tension





Factors 119864 119864119892

119871119901

119863 119864119901


119892is tensile



pile spacing


Factors 119864 119864119892

119871119901

119863 119864119901





0

10

20

30

40

at em

bank

men

t toe

(mm

)

0

20

40

60

80

100M

axim

um se

ttlem

ent (

mm

)

05 10 50 100

50

Late

ral d

ispla

cem

ent




0

20

40

60

80

100

Max

imum

tens

ion

(kN

m)


FGTCT

(b) Maximum tension




3 Cost Evaluation



4 Conclusions













Acknowledgments


References



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





0

10

20

30

40

at em

bank

men

t toe

(mm

)

0

20

40

60

80

100M

axim

um se

ttlem

ent (

mm

)

05 10 50 100

50

Late

ral d

ispla

cem

ent




0

20

40

60

80

100

Max

imum

tens

ion

(kN

m)


FGTCT

(b) Maximum tension




3 Cost Evaluation



4 Conclusions













Acknowledgments


References



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Acknowledgments


References



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Evaluation of an Improved Technique for...

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