Research ArticleSettlement Behavior of Soft Subgrade Reinforced byGeogrid-Encased Stone Column and Geocell-Embedded SandCushion A Numerical Analysis

Jia-Jun Gao 1 Hui Xu 1 Jian-Wen Qian 1 Yi-Fan Gong 1 Liang-Tong Zhan 2

and Ping Chen 1

1School of Civil Engineering and Architecture Zhejiang Sci-Tech University Hangzhou 310018 China2Department of Civil Engineering Zhejiang University Hangzhou 310058 China

Correspondence should be addressed to Hui Xu xuhuizstueducn

Received 21 August 2020 Revised 5 November 2020 Accepted 17 November 2020 Published 29 November 2020

Academic Editor Qiang Tang

Copyright copy 2020 Jia-Jun Gao et al is 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

e geosynthetic-encased vertical column and geosynthetic-embedded horizontal cushion are recognized as the effective methodsto reduce the settlement of the soft subgrade is paper investigated the settlement behavior of a soft subgrade reinforced bygeogrid-encased stone column and geocell-embedded sand cushion using the finite element analysis method (Plaxis 2D) esimulating settlement was in good agreement with the field monitoring data indicating the reasonability of the designed modeland adopted parameters After that the factors geocell layer in sand cushion encasement length around stone column andstanding time between embankment filling stages were employed to study their influences on the subgrade settlemente resultsshowed that the embedment of geocell reduced construction settlement postconstruction settlement and differential settlement isattributed to the increase in stiffness of sand cushion and therefore the uniform distribution of additional stress on subgradesurfaceWhen the encasement length of stone column increased from 1D (one time the column diameter) to 8D (full encasement)the settlement in construction stage and postconstruction stage decreased by 322 and 351 respectively which is benefitedfrom the increase in the compression modulus of the columnemaximum lateral deformation occurred at the position of about2D from the top of the stone column and it decreased more significantly when the encasement length increased from 1D to 4Dthan that from 4D to 8D e encasement length up to 4D is found to be adequate in reducing the subgrade settlement and thecolumn lateral deformation based on the consideration of performance and economy e extension of the filling intervalincreased the construction settlement caused by soil consolidation while it decreased the postconstruction settlement

1 Introduction

ere are large areas of soft soil ground distribution inChina especially in coastal regions as shown in Figure 1e soft soils are mostly silt silty clay and clay which havethe typical properties of being very low in stiffness very weakin shear strength and very small in hydraulic conductivity[1] Many infrastructure projects such as road embank-ments have been constructed in these regions In order tomeet the requirements of load-bearing capacity and settle-ment control of the subgrade the soft soil ground is nec-essary to be improved

ere are a number of techniques for the improvementof soft soil ground such as stone columns (granular piles)vacuum preconsolidation soil cement columns limetreatment [2] and foundation replacement [3ndash6] Among allthese methods the stone column technique is preferred dueto the advantages of increasing bearing capacity acceleratingconsolidation process reducing final settlement and beingrelatively cost-effective [7 8] However the construction ofstone columns in very soft soil with low undrained shearstrength is difficult due to insufficient lateral support of thesurrounding soil It is known that the most probable failuremechanism is bulging failure [7] which will lead to the

HindawiAdvances in Civil EngineeringVolume 2020 Article ID 8874520 11 pageshttpsdoiorg10115520208874520

destruction of the embankment [9ndash11] To solve the prob-lem the concept of geosynthetic-encased stone column(GESC) has been proposed in 1989 [2] e geosyntheticencasement could not only increase the strength of the stonecolumn and prevent the lateral squeezing of stones but alsoenable quicker and more economical installation [7]

In the recent decades many numerical and experimentalstudies have been carried out to focus on the performance ofGESC Fattah and Majeed [12ndash15] investigated the behaviorof soft soil ground reinforced with original stone column(OSC) and GESCe parameters different spacing distancebetween stone columns length to diameter ratio shearstrength of the surrounding soil and the area replacementratio were employed to study their effects on the bearingimprovement and settlement reduction Kwa et al [16]experimentally investigated the behavior of GESC forreinforcing of soft clay and found that the ultimate bearingcapacity of GESC is 16 times compared to OSC Malarvizhiand Ilamparuthi [17] conducted small-scale tests to inves-tigate the improved performance of GESC and found thatthe ultimate bearing capacity of GESC treated beds is threetimes that of the untreated beds Gu et al [18] also found thatthe ultimate load capacity of the soft soil was greatly in-creased by GESC and the effective length of the encasementwas three to four times of the diameter of stone columnsOrekanti and Dommaraju [8] conducted strain-restrictedcompression tests on GESC and the results showed thatGESC with lateral reinforcement of end-bearing type andfloating type showed a substantial increase in load-carryingcapacity relative to clay by 244 and 201 times respectivelyHajiazizi and Nasiri [19] experimentally investigated thebehavior of ordinary stone column (OSC) and GESC forreinforcing of sand slopes and found that location of GESCin middle of the slope increases the bearing capacity of slopecrown 217 times than OSC Ayadat andHanna [20] and Yooand Lee [21] performed experimental investigation on theload-carrying capacity and settlement of GESC and con-cluded that additional confinement provided by the

encasement not only increased the ultimate carrying ca-pacity of the stone column but also reduced the settlement ofthe soft ground as compared to conventional stone columnsSimilar results were also reported in the works of Murugesanand Rajagopal [7] and Kadhim et al [22] Almeida et al [23]presented the behavior and instrumentation results for a testembankment on soft soil improved by GESC and found thatthe differential settlement between column and surroundingsoil increased as the embankment height increased andconsolidation progressed

e previous studies have obtained many valuablefindings for a deep understanding of the performance ofGESC in improving the soft ground However most of thesestudies were carried out on a single GESC and the behaviorof GESC might be different in actual engineering In thisstudy the settlement behavior of a soft subgrade reinforcedwith GESC and geocell-embedded sand cushion was in-vestigated by using Plaxis 2D programe numerical modelwas verified using the monitoring data from a soft subgradeimprovement engineering A parametric study was thenconducted to study the influencing factors on the settlementbehavior of the soft subgrade including geocell layer in sandcushion encasement length around stone column andstanding time between embankment filling stages

2 Site Description

e selected case study for numerical modeling was a roadembankment of National Highway 320 in Hunan Chinawhich was constructed over deep soft soil e undergroundconditions of the site were reported in Zhou et alrsquos work[24] e geotechnical profile is characterized by an uppersoft soil layer extending to a depth of 6-7mis soft layer isdistributed with mainly silty clay which has extremely highwater content and very low shear strength Below the softlayer is a layer of coarse sand which is possible to induceliquefaction erefore both drainage and compactionshould be taken into account in the subgrade improvement

Soft soil

Soft soil

Soft soilSoft soil

Soft soil

Figure 1 Distribution of soft soil ground in China

2 Advances in Civil Engineering

e subgrade reinforcement program geogrid-encasedstone column and sand cushion were adopted in thisprojecte stone columns were 08m in diameter and 65min length with a spacing of 15m and area replacement rateof 56 Besides the stone columns were encased withgeogrid the encasement length was 15m approximatelytwice diameters of the stone column and the rest 5m of thestone column was not encased e sand cushion was 08min thickness which was used for horizontal drainage toaccelerate the consolidation of the subgrade

e filling process consists of three stages as shown inFigure 2 e filling height of each stage is 2me durationtime of filling is 6 d 8 d and 10 d for stage 1 stage 2 andstage 3 respectively e standing time is 10 d and 12 dbetween stages 1-2 and stages 2-3 respectively In this studythe duration of days 0ndash46 is regarded as the constructionstage and the duration of days 47ndash170 is the post-construction stage

3 Numerical Simulation

31 NumericalModel e finite element program Plaxis 2Dwas adopted to analyze the settlement behavior of thegeogrid-encased columns-supported embankment over softsoil e designed finite element model is shown in Figure 3e soil gravel and geogrid were modelled using a non-linear elastic-plastic constitutive model with Mohr-Cou-lomb yield criterion and the nonassociated flow rule All ofthe analyses were performed using meshes made up of four15-node triangles within each rectangle

e interface strength reduction factor (Rinter) was usedto simulate the interfacial interactions between geogrid andstone column as well as geogrid and surrounding soil evalue of Rinter was determined in reference to Wu and Hong[25] e geocell and the encased sand were treated as acomposite cell to simulate the reinforcement of geocell insand cushion is manner can not only simulate the me-chanical characteristics of geocell layers but also simplify themodelling steps and reduce the contact surface betweengeocell and sand [26] e deformation of bottom boundarywas fixed in both horizontal and vertical directions edeformation of the two side boundaries was fixed in thehorizontal direction but was allowed to move freely in thevertical direction

32Material Properties As reported in the work of Madhavi[27] the geocell-sand composite can be treated as anequivalent soil layer with cohesive strength greater than theencased soil and angle friction angle the same as the encasedsoil e induced cohesion in the soil cr is related to theincrease in the confining pressure on the soil due to geocellreinforcement which can be obtained through the followingequation

cr Δσ3

Kp

1113969

2 (1)

where Kp is the coefficient of passive Earth pressure and itcan be valued as 058 Δσ3 is the additional confining

pressure due to geocell reinforcement which can be cal-culated via the following equation

Δσ3 2M 1 minus

1 minus εa

11139681113872 1113873 1 minus εa( 11138571113960 1113961

D0 (2)

where εa is the axial strain at failure state and it can bevalued as 025 M is the secant modulus of the geocellmaterial at the axial strain of εa D0 is the initial diameter ofthe geocell and the value is 02256m in this study

Based on triaxial compression tests on geocell-encasedsand Madhavi [26] proposed the following empiricalequation to express Youngrsquos modulus of geocell-reinforcedsand (Eg)

Eg 4 σ3( 111385707

Ku + 200M016

1113872 1113873 (3)

where Ku is the dimensionless modulus parameter of theunreinforced sand and it can be valued as 025 M is thesecant modulus of the geocell material and the value shouldbe corresponded to the average strain of 25 in the load-elongation response of the geocell material here the value is160 kNm σ3 is the confining pressure and here the value is37 kPa

Based on the above method the cohesion and modulusof the geocell-sand composite can be obtained e physicaland mechanical parameters of embankment fill silty claysand and gravel were obtained from laboratory tests re-ported in the work of Zhou et al [24] e values of Rinterwere referenced from the work ofWu and Hong [25] All theparameters used in present numerical analysis are sum-marized in Table 1

33 Parametric Study e designed cases in present nu-merical analysis are shown in Table 2 Control case wascarried out on the actual engineering condition to verify thereliability and accuracy of the numerical model and adoptedparameters Case 1 was conducted by varying the number ofgeocell layers to investigate the effect of geocell layers in sandcushion on the settlement behavior of the subgrade In Case2 the encasement length of GESC was varied from 1D (onetime the stone column ie 08m) to 8D (full encasement

I3F3I2F2I1

Filli

ng h

eigh

t (m

)

F1

F filling stageI filling interval

Constructionstage Postconstruction stage

0

2

4

6

8

34 68 102 136 1700Elapsed time (d)

Figure 2 Filling process of the embankment

Advances in Civil Engineering 3

ie 64m) in order to study the influence of encasementlength on the settlement behavior of the subgrade einfluences of standing time between filling stages on thesubgrade settlement and pore water pressure were analyzedin Case 3 the filling interval was extended by 10 days 15days 20 days and 25 days in sequence on the basis of thecontrol case

4 Results and Analysis

41 Validation of Simulation Results Figure 4 shows thetemporal variation of surface settlement at the center of thesubgrade (point A) In the construction stage the simulatingsettlements at the end of F1 (day 6) I1 (day 16) F2 (day 24)I2 (day 36) and F3 (day 46) are 160 cm 254 cm 492 cm585 cm and 808 cm respectively and the correspondingfield monitoring settlements are 117 cm 257 cm 415 cm542 cm and 673 cm In the postconstruction stage after 124days following F3 the simulating settlement further de-veloped to 961 cm and the field monitoring result was944 cm It is observed that the simulated settlements areslightly larger than the measured results in the filling intervalstages that is I1 I2 and I3 e reason can be explained asfollows In the numerical analysis the subgrade soil wasassumed to be homogeneous and be classified into layers

that is an ideal state In fact the distribution of the subgradesoil was inhomogeneous and very complex in the field siteerefore the seepage path would be more flexural in thefield site which results in a lower hydraulic coefficient of thesubgrade soil and further leads to a delay of the consoli-dation settlement in the filling interval stages On the wholethe simulating results are quite comparable to the fieldmonitoring data which indicates that the designed nu-merical model and adopted parameters in this paper areacceptably accurate

42 Influence of Geocell Layers in Sand Cushion on the Sub-grade Settlement Figure 5 shows the temporal variation ofsurface settlement at the center of the subgrade (point A)when installing different layers of geocell in sand cushion Inthe construction stage the settlements increased to 735 cmand 667 cm respectively for the conditions of installation ofone-layer and two-layer geocell in sand cushion being 90and 175 smaller than the control case (no geocell layer)After 124 days following F3 the postconstruction settle-ments were 126 cm and 96 cm when installing one-layerand two-layer geocell respectively which are 192 and385 smaller than the control case It is observed that theembedment of geocell in sand cushion can significantly

Table 1 Physical and mechanical properties of the materials

Parameter Embankment fill Geocell-sand composite Silty clay Sand GravelNatural unit weight c (kNm3) 17 19 14 20 18Saturated unit weight csat (kNm3) 19 20 15 21 21Elasticity modulus E (MPa) 15 42 28 26 50Poissonrsquos ratio μ 03 03 035 03 03Cohesion c (kPa) 15 42 14 10 0Friction angle φ (deg) 23 30 17 30 35Interface strength reduction factor Rinter 065 065 058 058 058

Table 2 Designed cases in the finite-element simulations

Cases Geocell layer in sand cushion Encasement length of stone column Standing time between filling stagesControl case None 2D Actual engineering conditionCase 1 Onetwo 2D Actual engineering conditionCase 2 None 1Dsim8D Actual engineering conditionCase 3 None 2D +10 d + 15 d + 20 d + 25 dD refers to the diameter of the stone column

Embankment

Geocell reinforced sand cushion

Geogrid

Gravel pile

Sility clay64m

08m

28m Sand

Point A

Figure 3 Designed numerical model

4 Advances in Civil Engineering

reduce both the construction settlement and post-construction settlement of the subgrade

Figure 6 shows the differential settlement of the subgradeon day 170 under the conditions of installing different layersof geocell in sand cushion When there is no geocell layer in

the sand cushion the differential settlement between thecenter and the edge of the subgrade was about 730 cmWhen there is one geocell layer installed in the sand cushionthe differential settlement was about 660 cm being 96lower than the control case e differential settlement was

Filli

ng h

eigh

t (m

)Se

ttlem

ent o

f poi

ntA

(m)

Field monitoring resultsSimulating results (control case)

I3F3I2F2I1F1Construction stage Postconstruction stage

2

4

6

8

12

08

04

00

34 68 102 136 1700Elapsed time (d)

Figure 4 Comparison between monitoring and simulating results for the settlement of point A

I3F3I2F2I1F1Construction stage Postconstruction stage

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Filli

ng h

eigh

t (m

)Se

ttlem

ent o

f poi

ntA

(m)

2

4

6

8

10

08

06

04

02

00

34 68 102 136 1700 Elapsed time (d)

Figure 5 Influence of geocell layer in sand cushion on the settlement of point A

Advances in Civil Engineering 5

about 591 cm when installing two-layer geocell being 190lower than the control case It can be seen that the em-bedment of geocell in sand cushion can effectively reduce thedifferential settlement of the subgrade

43 Influence of Encasement Length of Stone Column on theSubgrade Settlement and Column Lateral DeformationFigure 7 shows the temporal variation of surface settle-ment at the center of the subgrade (point A) with differentencasement length of the stone column In the con-struction stage the settlements increased to 888 cm808 cm 753 cm 707 cm 679 cm 650 cm 628 cm and602 cm with respect to the encasement length of 1D 2D3D 4D 5D 6D 7D and 8D (full encasement) In thepostconstruction stage after 124 days following F3 thesettlements further developed to 1047 cm 961 cm885 cm 820 cm 779 cm 741 cm 708 cm and 679 cmfor the encasement length of 1D 2D 3D 4D 5D 6D 7Dand 8D respectively corresponding to the post-construction settlements of 159 cm 153 cm 132 cm113 cm 100 cm 91 cm 80 cm and 77 cm It is seen thatthe increase of encasement length of the stone columnresults in the reductions of both construction and post-construction settlements of the subgrade It is also ob-served that the settlement decreased more significantlywith the encasement length increasing from 1D to 4Dhowever a further increase of the encasement lengthresulted in a slow decrease of the settlement erefore theencasement length of the stone column up to four times ofthe diameter of the column is found to be adequate in

reducing the settlement based on the consideration ofperformance and economy

Figure 8 shows the differential settlement of the subgradeon day 170 with different encasement length of the stonecolumn When the encasement length was 1D the differ-ential settlement between the center and the edge of sub-grade was about 781 cm If the encasement length increasedto 4D the differential settlement was about 619 cm and thereduction rate was about 207 regarding 1D condition Ifthe encasement length further increased to 8D the differ-ential settlement was about 517 cm corresponding to areduction rate of 338 when compared to 1D condition Itcan be seen that the differential settlement of the subgradegradually decreases significantly with the increase of theencasement length of the stone column

Taking the stone column at the center of the subgrade asan example the lateral deformations of the stone columnwith different encasement lengths are shown in Figure 9elateral deformations were calculated at day 170 that is 124days after the completion of the embankment filling It isobserved that the maximum lateral deformation occurs atthe position of about 2D from the top of the stone columnand it decreases gradually with the increase of encasementlength of the stone column When the encasement length is1D the maximum lateral deformation is about 920 cmWhen the encasement length increases to 4D and 8D themaximum lateral deformation is about 367 cm and 275 cmrespectively corresponding to a reduction rate of 6008and 7008 when compared to 1D condition It is seen thatthe lateral deformation decreased more significantly whenthe encasement length increased from 1D to 4D compared to

Filli

nghe

ight

(m)

Embankment

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Settl

emen

t (m

)

0

2

4

6

10

08

06

04

02

00

5 10 15 20 250Distance from the subgradecenter (m)

Figure 6 Influence of geocell layer in sand cushion on the differential settlement

6 Advances in Civil Engineering

Embankment

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

5 10 15 20 250Distance from the subgradecenter (m)

Filli

nghe

ight

(m)

Settl

emen

t (m

)

12

09

06

03

00

2

4

6

Figure 8 Influence of encasement length on the differential settlement

I3F3I2F2I1F1Construction stage Postconstruction stage

Filli

ng h

eigh

t (m

)

2

4

6

8

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

Settl

emen

t of p

oint

A (m

)

12

09

06

03

00

34 68 102 136 1700Elapsed time (d)

Figure 7 Influence of encasement length on the settlement of point A

Advances in Civil Engineering 7

that from 4D to 8D erefore the encasement length of thestone column up to 4D is found to be adequate in reducingthe lateral deformation of the column when consideringboth the performance and economy

44 Influence of Filling Interval on the Subgrade SettlementFigure 10 shows the temporal variation of surface settlementat the center of the subgrade (point A) with different

standing time between filling stages In the constructionstage the settlement developed rapidly and the excess porewater pressure increased sharply during the filling processand the settlement developed slowly and the excess porewater pressure gradually dissipated in the standing periodIn this stage the settlements developed to 830 cm 836 cm841 cm and 845 cm respectively for the filling intervalextended by 10 days 15 days 20 days and 25 days being

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Settl

emen

t of

poin

t A (m

)

10

08

06

04

02

00

44 88 132 176 2200Elapsed time (d)

Exce

ss p

ore p

ress

ure

of p

oint

A (k

Pa)

7

14

21

28

Filli

ng h

eigh

t (m

)

4

2

0

6

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 10 Influence of filling interval on excess pore water pressure and settlement of point A

Burie

d de

pth

of G

ESC

(m)

1D2D3D4D

5D6D7D8D

60

45

30

15

00

5 10 150Lateral deformation of GESC (cm)

Figure 9 Influence of encasement length on the lateral deformation

8 Advances in Civil Engineering

31 39 45 and 50 larger than the control case Inthe postconstruction stage the settlement further developedto a stable value and the excess pore water pressure graduallydissipated to approximately zero e postconstructionsettlements were 134 cm 130 cm 126 cm and 122 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days being 141 167 196 and218 smaller than the control case It is seen that the ex-tension of the filling interval will promote the consolidationof subgrade soil in the construction stage which results in anincrease in the construction settlement and a reduction inthe postconstruction settlement

Figure 11 shows the differential settlement of the sub-grade with different standing time between filling stagesesettlements were calculated at the time point of 124 daysafter the completion of the embankment filling e dif-ferential settlements between the center and the edge of thesubgrade were about 739 cm 741 cm 744 cm and 745 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days the corresponding increase rateswere about 12 15 19 and 21 when compared tothe control case It can be seen that the extension of thestanding time between filling stages has negligible influenceon the differential settlement of the subgrade

5 Discussion

Composite compression modulus method is one of theavailable methods to compute the settlement of GESCsupported composite foundation and the calculationequation [28] is presented as follows

S 1113944n

i1

Δpi

EcsiHi

Ecs mEps +(1 minus m)Ess

(4)

where S is final settlement of composite foundation Ess iscompression modulus of the soil Eps is compressionmodulus of the column Ecs is composite compressionmodulus of the foundationm is area replacement ratio n arenumbers of calculation layers Hi is thickness of soil layer iDpi is additional stress of soil layer i From the aboveequation the following issues were discussed

(1) e embedment of geocell would provide rein-forcement via the restriction of soil movement andthe concentration of stresses within the geocellhence increasing the stiffness of the sand cushion[29] In addition the confinement provided bygeocells improves the distribution of additionalstress over the subgrade [30] and decreases more atthe center and decreases less at the side [31] As aresult both the center settlement and differentialsettlement on the subgrade surface reduce [30]

(2) e lateral deformation of the stone column de-creased due to the additional confining stress pro-vided by the geogrid encasement and therefore thecompression modulus of the column increases aswell as the composite compression modulus of thefoundation [22 32] As a result the larger the en-casement length of the column the smaller the

Filli

nghe

ight

(m)

Embankment

00 09 18 27 36097

096

095

094

Settl

emen

t (m

)

2

4

6

09

06

03

00

5 10 15 20 250Distance from the subgrade center (m)

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)

Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 11 Influence of filling interval on the differential settlement

Advances in Civil Engineering 9

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

e subgrade reinforcement program geogrid-encasedstone column and sand cushion were adopted in thisprojecte stone columns were 08m in diameter and 65min length with a spacing of 15m and area replacement rateof 56 Besides the stone columns were encased withgeogrid the encasement length was 15m approximatelytwice diameters of the stone column and the rest 5m of thestone column was not encased e sand cushion was 08min thickness which was used for horizontal drainage toaccelerate the consolidation of the subgrade

e filling process consists of three stages as shown inFigure 2 e filling height of each stage is 2me durationtime of filling is 6 d 8 d and 10 d for stage 1 stage 2 andstage 3 respectively e standing time is 10 d and 12 dbetween stages 1-2 and stages 2-3 respectively In this studythe duration of days 0ndash46 is regarded as the constructionstage and the duration of days 47ndash170 is the post-construction stage

3 Numerical Simulation

31 NumericalModel e finite element program Plaxis 2Dwas adopted to analyze the settlement behavior of thegeogrid-encased columns-supported embankment over softsoil e designed finite element model is shown in Figure 3e soil gravel and geogrid were modelled using a non-linear elastic-plastic constitutive model with Mohr-Cou-lomb yield criterion and the nonassociated flow rule All ofthe analyses were performed using meshes made up of four15-node triangles within each rectangle

e interface strength reduction factor (Rinter) was usedto simulate the interfacial interactions between geogrid andstone column as well as geogrid and surrounding soil evalue of Rinter was determined in reference to Wu and Hong[25] e geocell and the encased sand were treated as acomposite cell to simulate the reinforcement of geocell insand cushion is manner can not only simulate the me-chanical characteristics of geocell layers but also simplify themodelling steps and reduce the contact surface betweengeocell and sand [26] e deformation of bottom boundarywas fixed in both horizontal and vertical directions edeformation of the two side boundaries was fixed in thehorizontal direction but was allowed to move freely in thevertical direction

32Material Properties As reported in the work of Madhavi[27] the geocell-sand composite can be treated as anequivalent soil layer with cohesive strength greater than theencased soil and angle friction angle the same as the encasedsoil e induced cohesion in the soil cr is related to theincrease in the confining pressure on the soil due to geocellreinforcement which can be obtained through the followingequation

cr Δσ3

Kp

1113969

2 (1)

where Kp is the coefficient of passive Earth pressure and itcan be valued as 058 Δσ3 is the additional confining

pressure due to geocell reinforcement which can be cal-culated via the following equation

Δσ3 2M 1 minus

1 minus εa

11139681113872 1113873 1 minus εa( 11138571113960 1113961

D0 (2)

where εa is the axial strain at failure state and it can bevalued as 025 M is the secant modulus of the geocellmaterial at the axial strain of εa D0 is the initial diameter ofthe geocell and the value is 02256m in this study

Based on triaxial compression tests on geocell-encasedsand Madhavi [26] proposed the following empiricalequation to express Youngrsquos modulus of geocell-reinforcedsand (Eg)

Eg 4 σ3( 111385707

Ku + 200M016

1113872 1113873 (3)

where Ku is the dimensionless modulus parameter of theunreinforced sand and it can be valued as 025 M is thesecant modulus of the geocell material and the value shouldbe corresponded to the average strain of 25 in the load-elongation response of the geocell material here the value is160 kNm σ3 is the confining pressure and here the value is37 kPa

Based on the above method the cohesion and modulusof the geocell-sand composite can be obtained e physicaland mechanical parameters of embankment fill silty claysand and gravel were obtained from laboratory tests re-ported in the work of Zhou et al [24] e values of Rinterwere referenced from the work ofWu and Hong [25] All theparameters used in present numerical analysis are sum-marized in Table 1

33 Parametric Study e designed cases in present nu-merical analysis are shown in Table 2 Control case wascarried out on the actual engineering condition to verify thereliability and accuracy of the numerical model and adoptedparameters Case 1 was conducted by varying the number ofgeocell layers to investigate the effect of geocell layers in sandcushion on the settlement behavior of the subgrade In Case2 the encasement length of GESC was varied from 1D (onetime the stone column ie 08m) to 8D (full encasement

I3F3I2F2I1

Filli

ng h

eigh

t (m

)

F1

F filling stageI filling interval

Constructionstage Postconstruction stage

0

2

4

6

8

34 68 102 136 1700Elapsed time (d)

Figure 2 Filling process of the embankment

Advances in Civil Engineering 3

ie 64m) in order to study the influence of encasementlength on the settlement behavior of the subgrade einfluences of standing time between filling stages on thesubgrade settlement and pore water pressure were analyzedin Case 3 the filling interval was extended by 10 days 15days 20 days and 25 days in sequence on the basis of thecontrol case

4 Results and Analysis

41 Validation of Simulation Results Figure 4 shows thetemporal variation of surface settlement at the center of thesubgrade (point A) In the construction stage the simulatingsettlements at the end of F1 (day 6) I1 (day 16) F2 (day 24)I2 (day 36) and F3 (day 46) are 160 cm 254 cm 492 cm585 cm and 808 cm respectively and the correspondingfield monitoring settlements are 117 cm 257 cm 415 cm542 cm and 673 cm In the postconstruction stage after 124days following F3 the simulating settlement further de-veloped to 961 cm and the field monitoring result was944 cm It is observed that the simulated settlements areslightly larger than the measured results in the filling intervalstages that is I1 I2 and I3 e reason can be explained asfollows In the numerical analysis the subgrade soil wasassumed to be homogeneous and be classified into layers

that is an ideal state In fact the distribution of the subgradesoil was inhomogeneous and very complex in the field siteerefore the seepage path would be more flexural in thefield site which results in a lower hydraulic coefficient of thesubgrade soil and further leads to a delay of the consoli-dation settlement in the filling interval stages On the wholethe simulating results are quite comparable to the fieldmonitoring data which indicates that the designed nu-merical model and adopted parameters in this paper areacceptably accurate

42 Influence of Geocell Layers in Sand Cushion on the Sub-grade Settlement Figure 5 shows the temporal variation ofsurface settlement at the center of the subgrade (point A)when installing different layers of geocell in sand cushion Inthe construction stage the settlements increased to 735 cmand 667 cm respectively for the conditions of installation ofone-layer and two-layer geocell in sand cushion being 90and 175 smaller than the control case (no geocell layer)After 124 days following F3 the postconstruction settle-ments were 126 cm and 96 cm when installing one-layerand two-layer geocell respectively which are 192 and385 smaller than the control case It is observed that theembedment of geocell in sand cushion can significantly

Table 1 Physical and mechanical properties of the materials

Parameter Embankment fill Geocell-sand composite Silty clay Sand GravelNatural unit weight c (kNm3) 17 19 14 20 18Saturated unit weight csat (kNm3) 19 20 15 21 21Elasticity modulus E (MPa) 15 42 28 26 50Poissonrsquos ratio μ 03 03 035 03 03Cohesion c (kPa) 15 42 14 10 0Friction angle φ (deg) 23 30 17 30 35Interface strength reduction factor Rinter 065 065 058 058 058

Table 2 Designed cases in the finite-element simulations

Cases Geocell layer in sand cushion Encasement length of stone column Standing time between filling stagesControl case None 2D Actual engineering conditionCase 1 Onetwo 2D Actual engineering conditionCase 2 None 1Dsim8D Actual engineering conditionCase 3 None 2D +10 d + 15 d + 20 d + 25 dD refers to the diameter of the stone column

Embankment

Geocell reinforced sand cushion

Geogrid

Gravel pile

Sility clay64m

08m

28m Sand

Point A

Figure 3 Designed numerical model

4 Advances in Civil Engineering

reduce both the construction settlement and post-construction settlement of the subgrade

Figure 6 shows the differential settlement of the subgradeon day 170 under the conditions of installing different layersof geocell in sand cushion When there is no geocell layer in

the sand cushion the differential settlement between thecenter and the edge of the subgrade was about 730 cmWhen there is one geocell layer installed in the sand cushionthe differential settlement was about 660 cm being 96lower than the control case e differential settlement was

Filli

ng h

eigh

t (m

)Se

ttlem

ent o

f poi

ntA

(m)

Field monitoring resultsSimulating results (control case)

I3F3I2F2I1F1Construction stage Postconstruction stage

2

4

6

8

12

08

04

00

34 68 102 136 1700Elapsed time (d)

Figure 4 Comparison between monitoring and simulating results for the settlement of point A

I3F3I2F2I1F1Construction stage Postconstruction stage

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Filli

ng h

eigh

t (m

)Se

ttlem

ent o

f poi

ntA

(m)

2

4

6

8

10

08

06

04

02

00

34 68 102 136 1700 Elapsed time (d)

Figure 5 Influence of geocell layer in sand cushion on the settlement of point A

Advances in Civil Engineering 5

about 591 cm when installing two-layer geocell being 190lower than the control case It can be seen that the em-bedment of geocell in sand cushion can effectively reduce thedifferential settlement of the subgrade

43 Influence of Encasement Length of Stone Column on theSubgrade Settlement and Column Lateral DeformationFigure 7 shows the temporal variation of surface settle-ment at the center of the subgrade (point A) with differentencasement length of the stone column In the con-struction stage the settlements increased to 888 cm808 cm 753 cm 707 cm 679 cm 650 cm 628 cm and602 cm with respect to the encasement length of 1D 2D3D 4D 5D 6D 7D and 8D (full encasement) In thepostconstruction stage after 124 days following F3 thesettlements further developed to 1047 cm 961 cm885 cm 820 cm 779 cm 741 cm 708 cm and 679 cmfor the encasement length of 1D 2D 3D 4D 5D 6D 7Dand 8D respectively corresponding to the post-construction settlements of 159 cm 153 cm 132 cm113 cm 100 cm 91 cm 80 cm and 77 cm It is seen thatthe increase of encasement length of the stone columnresults in the reductions of both construction and post-construction settlements of the subgrade It is also ob-served that the settlement decreased more significantlywith the encasement length increasing from 1D to 4Dhowever a further increase of the encasement lengthresulted in a slow decrease of the settlement erefore theencasement length of the stone column up to four times ofthe diameter of the column is found to be adequate in

reducing the settlement based on the consideration ofperformance and economy

Figure 8 shows the differential settlement of the subgradeon day 170 with different encasement length of the stonecolumn When the encasement length was 1D the differ-ential settlement between the center and the edge of sub-grade was about 781 cm If the encasement length increasedto 4D the differential settlement was about 619 cm and thereduction rate was about 207 regarding 1D condition Ifthe encasement length further increased to 8D the differ-ential settlement was about 517 cm corresponding to areduction rate of 338 when compared to 1D condition Itcan be seen that the differential settlement of the subgradegradually decreases significantly with the increase of theencasement length of the stone column

Taking the stone column at the center of the subgrade asan example the lateral deformations of the stone columnwith different encasement lengths are shown in Figure 9elateral deformations were calculated at day 170 that is 124days after the completion of the embankment filling It isobserved that the maximum lateral deformation occurs atthe position of about 2D from the top of the stone columnand it decreases gradually with the increase of encasementlength of the stone column When the encasement length is1D the maximum lateral deformation is about 920 cmWhen the encasement length increases to 4D and 8D themaximum lateral deformation is about 367 cm and 275 cmrespectively corresponding to a reduction rate of 6008and 7008 when compared to 1D condition It is seen thatthe lateral deformation decreased more significantly whenthe encasement length increased from 1D to 4D compared to

Filli

nghe

ight

(m)

Embankment

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Settl

emen

t (m

)

0

2

4

6

10

08

06

04

02

00

5 10 15 20 250Distance from the subgradecenter (m)

Figure 6 Influence of geocell layer in sand cushion on the differential settlement

6 Advances in Civil Engineering

Embankment

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

5 10 15 20 250Distance from the subgradecenter (m)

Filli

nghe

ight

(m)

Settl

emen

t (m

)

12

09

06

03

00

2

4

6

Figure 8 Influence of encasement length on the differential settlement

I3F3I2F2I1F1Construction stage Postconstruction stage

Filli

ng h

eigh

t (m

)

2

4

6

8

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

Settl

emen

t of p

oint

A (m

)

12

09

06

03

00

34 68 102 136 1700Elapsed time (d)

Figure 7 Influence of encasement length on the settlement of point A

Advances in Civil Engineering 7

that from 4D to 8D erefore the encasement length of thestone column up to 4D is found to be adequate in reducingthe lateral deformation of the column when consideringboth the performance and economy

44 Influence of Filling Interval on the Subgrade SettlementFigure 10 shows the temporal variation of surface settlementat the center of the subgrade (point A) with different

standing time between filling stages In the constructionstage the settlement developed rapidly and the excess porewater pressure increased sharply during the filling processand the settlement developed slowly and the excess porewater pressure gradually dissipated in the standing periodIn this stage the settlements developed to 830 cm 836 cm841 cm and 845 cm respectively for the filling intervalextended by 10 days 15 days 20 days and 25 days being

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Settl

emen

t of

poin

t A (m

)

10

08

06

04

02

00

44 88 132 176 2200Elapsed time (d)

Exce

ss p

ore p

ress

ure

of p

oint

A (k

Pa)

7

14

21

28

Filli

ng h

eigh

t (m

)

4

2

0

6

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 10 Influence of filling interval on excess pore water pressure and settlement of point A

Burie

d de

pth

of G

ESC

(m)

1D2D3D4D

5D6D7D8D

60

45

30

15

00

5 10 150Lateral deformation of GESC (cm)

Figure 9 Influence of encasement length on the lateral deformation

8 Advances in Civil Engineering

31 39 45 and 50 larger than the control case Inthe postconstruction stage the settlement further developedto a stable value and the excess pore water pressure graduallydissipated to approximately zero e postconstructionsettlements were 134 cm 130 cm 126 cm and 122 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days being 141 167 196 and218 smaller than the control case It is seen that the ex-tension of the filling interval will promote the consolidationof subgrade soil in the construction stage which results in anincrease in the construction settlement and a reduction inthe postconstruction settlement

Figure 11 shows the differential settlement of the sub-grade with different standing time between filling stagesesettlements were calculated at the time point of 124 daysafter the completion of the embankment filling e dif-ferential settlements between the center and the edge of thesubgrade were about 739 cm 741 cm 744 cm and 745 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days the corresponding increase rateswere about 12 15 19 and 21 when compared tothe control case It can be seen that the extension of thestanding time between filling stages has negligible influenceon the differential settlement of the subgrade

5 Discussion

Composite compression modulus method is one of theavailable methods to compute the settlement of GESCsupported composite foundation and the calculationequation [28] is presented as follows

S 1113944n

i1

Δpi

EcsiHi

Ecs mEps +(1 minus m)Ess

(4)

where S is final settlement of composite foundation Ess iscompression modulus of the soil Eps is compressionmodulus of the column Ecs is composite compressionmodulus of the foundationm is area replacement ratio n arenumbers of calculation layers Hi is thickness of soil layer iDpi is additional stress of soil layer i From the aboveequation the following issues were discussed

(1) e embedment of geocell would provide rein-forcement via the restriction of soil movement andthe concentration of stresses within the geocellhence increasing the stiffness of the sand cushion[29] In addition the confinement provided bygeocells improves the distribution of additionalstress over the subgrade [30] and decreases more atthe center and decreases less at the side [31] As aresult both the center settlement and differentialsettlement on the subgrade surface reduce [30]

(2) e lateral deformation of the stone column de-creased due to the additional confining stress pro-vided by the geogrid encasement and therefore thecompression modulus of the column increases aswell as the composite compression modulus of thefoundation [22 32] As a result the larger the en-casement length of the column the smaller the

Filli

nghe

ight

(m)

Embankment

00 09 18 27 36097

096

095

094

Settl

emen

t (m

)

2

4

6

09

06

03

00

5 10 15 20 250Distance from the subgrade center (m)

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)

Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 11 Influence of filling interval on the differential settlement

Advances in Civil Engineering 9

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

ie 64m) in order to study the influence of encasementlength on the settlement behavior of the subgrade einfluences of standing time between filling stages on thesubgrade settlement and pore water pressure were analyzedin Case 3 the filling interval was extended by 10 days 15days 20 days and 25 days in sequence on the basis of thecontrol case

4 Results and Analysis

41 Validation of Simulation Results Figure 4 shows thetemporal variation of surface settlement at the center of thesubgrade (point A) In the construction stage the simulatingsettlements at the end of F1 (day 6) I1 (day 16) F2 (day 24)I2 (day 36) and F3 (day 46) are 160 cm 254 cm 492 cm585 cm and 808 cm respectively and the correspondingfield monitoring settlements are 117 cm 257 cm 415 cm542 cm and 673 cm In the postconstruction stage after 124days following F3 the simulating settlement further de-veloped to 961 cm and the field monitoring result was944 cm It is observed that the simulated settlements areslightly larger than the measured results in the filling intervalstages that is I1 I2 and I3 e reason can be explained asfollows In the numerical analysis the subgrade soil wasassumed to be homogeneous and be classified into layers

that is an ideal state In fact the distribution of the subgradesoil was inhomogeneous and very complex in the field siteerefore the seepage path would be more flexural in thefield site which results in a lower hydraulic coefficient of thesubgrade soil and further leads to a delay of the consoli-dation settlement in the filling interval stages On the wholethe simulating results are quite comparable to the fieldmonitoring data which indicates that the designed nu-merical model and adopted parameters in this paper areacceptably accurate

42 Influence of Geocell Layers in Sand Cushion on the Sub-grade Settlement Figure 5 shows the temporal variation ofsurface settlement at the center of the subgrade (point A)when installing different layers of geocell in sand cushion Inthe construction stage the settlements increased to 735 cmand 667 cm respectively for the conditions of installation ofone-layer and two-layer geocell in sand cushion being 90and 175 smaller than the control case (no geocell layer)After 124 days following F3 the postconstruction settle-ments were 126 cm and 96 cm when installing one-layerand two-layer geocell respectively which are 192 and385 smaller than the control case It is observed that theembedment of geocell in sand cushion can significantly

Table 1 Physical and mechanical properties of the materials

Parameter Embankment fill Geocell-sand composite Silty clay Sand GravelNatural unit weight c (kNm3) 17 19 14 20 18Saturated unit weight csat (kNm3) 19 20 15 21 21Elasticity modulus E (MPa) 15 42 28 26 50Poissonrsquos ratio μ 03 03 035 03 03Cohesion c (kPa) 15 42 14 10 0Friction angle φ (deg) 23 30 17 30 35Interface strength reduction factor Rinter 065 065 058 058 058

Table 2 Designed cases in the finite-element simulations

Cases Geocell layer in sand cushion Encasement length of stone column Standing time between filling stagesControl case None 2D Actual engineering conditionCase 1 Onetwo 2D Actual engineering conditionCase 2 None 1Dsim8D Actual engineering conditionCase 3 None 2D +10 d + 15 d + 20 d + 25 dD refers to the diameter of the stone column

Embankment

Geocell reinforced sand cushion

Geogrid

Gravel pile

Sility clay64m

08m

28m Sand

Point A

Figure 3 Designed numerical model

4 Advances in Civil Engineering

reduce both the construction settlement and post-construction settlement of the subgrade

Figure 6 shows the differential settlement of the subgradeon day 170 under the conditions of installing different layersof geocell in sand cushion When there is no geocell layer in

the sand cushion the differential settlement between thecenter and the edge of the subgrade was about 730 cmWhen there is one geocell layer installed in the sand cushionthe differential settlement was about 660 cm being 96lower than the control case e differential settlement was

Filli

ng h

eigh

t (m

)Se

ttlem

ent o

f poi

ntA

(m)

Field monitoring resultsSimulating results (control case)

I3F3I2F2I1F1Construction stage Postconstruction stage

2

4

6

8

12

08

04

00

34 68 102 136 1700Elapsed time (d)

Figure 4 Comparison between monitoring and simulating results for the settlement of point A

I3F3I2F2I1F1Construction stage Postconstruction stage

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Filli

ng h

eigh

t (m

)Se

ttlem

ent o

f poi

ntA

(m)

2

4

6

8

10

08

06

04

02

00

34 68 102 136 1700 Elapsed time (d)

Figure 5 Influence of geocell layer in sand cushion on the settlement of point A

Advances in Civil Engineering 5

about 591 cm when installing two-layer geocell being 190lower than the control case It can be seen that the em-bedment of geocell in sand cushion can effectively reduce thedifferential settlement of the subgrade

43 Influence of Encasement Length of Stone Column on theSubgrade Settlement and Column Lateral DeformationFigure 7 shows the temporal variation of surface settle-ment at the center of the subgrade (point A) with differentencasement length of the stone column In the con-struction stage the settlements increased to 888 cm808 cm 753 cm 707 cm 679 cm 650 cm 628 cm and602 cm with respect to the encasement length of 1D 2D3D 4D 5D 6D 7D and 8D (full encasement) In thepostconstruction stage after 124 days following F3 thesettlements further developed to 1047 cm 961 cm885 cm 820 cm 779 cm 741 cm 708 cm and 679 cmfor the encasement length of 1D 2D 3D 4D 5D 6D 7Dand 8D respectively corresponding to the post-construction settlements of 159 cm 153 cm 132 cm113 cm 100 cm 91 cm 80 cm and 77 cm It is seen thatthe increase of encasement length of the stone columnresults in the reductions of both construction and post-construction settlements of the subgrade It is also ob-served that the settlement decreased more significantlywith the encasement length increasing from 1D to 4Dhowever a further increase of the encasement lengthresulted in a slow decrease of the settlement erefore theencasement length of the stone column up to four times ofthe diameter of the column is found to be adequate in

reducing the settlement based on the consideration ofperformance and economy

Figure 8 shows the differential settlement of the subgradeon day 170 with different encasement length of the stonecolumn When the encasement length was 1D the differ-ential settlement between the center and the edge of sub-grade was about 781 cm If the encasement length increasedto 4D the differential settlement was about 619 cm and thereduction rate was about 207 regarding 1D condition Ifthe encasement length further increased to 8D the differ-ential settlement was about 517 cm corresponding to areduction rate of 338 when compared to 1D condition Itcan be seen that the differential settlement of the subgradegradually decreases significantly with the increase of theencasement length of the stone column

Taking the stone column at the center of the subgrade asan example the lateral deformations of the stone columnwith different encasement lengths are shown in Figure 9elateral deformations were calculated at day 170 that is 124days after the completion of the embankment filling It isobserved that the maximum lateral deformation occurs atthe position of about 2D from the top of the stone columnand it decreases gradually with the increase of encasementlength of the stone column When the encasement length is1D the maximum lateral deformation is about 920 cmWhen the encasement length increases to 4D and 8D themaximum lateral deformation is about 367 cm and 275 cmrespectively corresponding to a reduction rate of 6008and 7008 when compared to 1D condition It is seen thatthe lateral deformation decreased more significantly whenthe encasement length increased from 1D to 4D compared to

Filli

nghe

ight

(m)

Embankment

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Settl

emen

t (m

)

0

2

4

6

10

08

06

04

02

00

5 10 15 20 250Distance from the subgradecenter (m)

Figure 6 Influence of geocell layer in sand cushion on the differential settlement

6 Advances in Civil Engineering

Embankment

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

5 10 15 20 250Distance from the subgradecenter (m)

Filli

nghe

ight

(m)

Settl

emen

t (m

)

12

09

06

03

00

2

4

6

Figure 8 Influence of encasement length on the differential settlement

I3F3I2F2I1F1Construction stage Postconstruction stage

Filli

ng h

eigh

t (m

)

2

4

6

8

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

Settl

emen

t of p

oint

A (m

)

12

09

06

03

00

34 68 102 136 1700Elapsed time (d)

Figure 7 Influence of encasement length on the settlement of point A

Advances in Civil Engineering 7

that from 4D to 8D erefore the encasement length of thestone column up to 4D is found to be adequate in reducingthe lateral deformation of the column when consideringboth the performance and economy

44 Influence of Filling Interval on the Subgrade SettlementFigure 10 shows the temporal variation of surface settlementat the center of the subgrade (point A) with different

standing time between filling stages In the constructionstage the settlement developed rapidly and the excess porewater pressure increased sharply during the filling processand the settlement developed slowly and the excess porewater pressure gradually dissipated in the standing periodIn this stage the settlements developed to 830 cm 836 cm841 cm and 845 cm respectively for the filling intervalextended by 10 days 15 days 20 days and 25 days being

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Settl

emen

t of

poin

t A (m

)

10

08

06

04

02

00

44 88 132 176 2200Elapsed time (d)

Exce

ss p

ore p

ress

ure

of p

oint

A (k

Pa)

7

14

21

28

Filli

ng h

eigh

t (m

)

4

2

0

6

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 10 Influence of filling interval on excess pore water pressure and settlement of point A

Burie

d de

pth

of G

ESC

(m)

1D2D3D4D

5D6D7D8D

60

45

30

15

00

5 10 150Lateral deformation of GESC (cm)

Figure 9 Influence of encasement length on the lateral deformation

8 Advances in Civil Engineering

31 39 45 and 50 larger than the control case Inthe postconstruction stage the settlement further developedto a stable value and the excess pore water pressure graduallydissipated to approximately zero e postconstructionsettlements were 134 cm 130 cm 126 cm and 122 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days being 141 167 196 and218 smaller than the control case It is seen that the ex-tension of the filling interval will promote the consolidationof subgrade soil in the construction stage which results in anincrease in the construction settlement and a reduction inthe postconstruction settlement

Figure 11 shows the differential settlement of the sub-grade with different standing time between filling stagesesettlements were calculated at the time point of 124 daysafter the completion of the embankment filling e dif-ferential settlements between the center and the edge of thesubgrade were about 739 cm 741 cm 744 cm and 745 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days the corresponding increase rateswere about 12 15 19 and 21 when compared tothe control case It can be seen that the extension of thestanding time between filling stages has negligible influenceon the differential settlement of the subgrade

5 Discussion

Composite compression modulus method is one of theavailable methods to compute the settlement of GESCsupported composite foundation and the calculationequation [28] is presented as follows

S 1113944n

i1

Δpi

EcsiHi

Ecs mEps +(1 minus m)Ess

(4)

where S is final settlement of composite foundation Ess iscompression modulus of the soil Eps is compressionmodulus of the column Ecs is composite compressionmodulus of the foundationm is area replacement ratio n arenumbers of calculation layers Hi is thickness of soil layer iDpi is additional stress of soil layer i From the aboveequation the following issues were discussed

(1) e embedment of geocell would provide rein-forcement via the restriction of soil movement andthe concentration of stresses within the geocellhence increasing the stiffness of the sand cushion[29] In addition the confinement provided bygeocells improves the distribution of additionalstress over the subgrade [30] and decreases more atthe center and decreases less at the side [31] As aresult both the center settlement and differentialsettlement on the subgrade surface reduce [30]

(2) e lateral deformation of the stone column de-creased due to the additional confining stress pro-vided by the geogrid encasement and therefore thecompression modulus of the column increases aswell as the composite compression modulus of thefoundation [22 32] As a result the larger the en-casement length of the column the smaller the

Filli

nghe

ight

(m)

Embankment

00 09 18 27 36097

096

095

094

Settl

emen

t (m

)

2

4

6

09

06

03

00

5 10 15 20 250Distance from the subgrade center (m)

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)

Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 11 Influence of filling interval on the differential settlement

Advances in Civil Engineering 9

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

reduce both the construction settlement and post-construction settlement of the subgrade

Figure 6 shows the differential settlement of the subgradeon day 170 under the conditions of installing different layersof geocell in sand cushion When there is no geocell layer in

the sand cushion the differential settlement between thecenter and the edge of the subgrade was about 730 cmWhen there is one geocell layer installed in the sand cushionthe differential settlement was about 660 cm being 96lower than the control case e differential settlement was

Filli

ng h

eigh

t (m

)Se

ttlem

ent o

f poi

ntA

(m)

Field monitoring resultsSimulating results (control case)

I3F3I2F2I1F1Construction stage Postconstruction stage

2

4

6

8

12

08

04

00

34 68 102 136 1700Elapsed time (d)

Figure 4 Comparison between monitoring and simulating results for the settlement of point A

I3F3I2F2I1F1Construction stage Postconstruction stage

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Filli

ng h

eigh

t (m

)Se

ttlem

ent o

f poi

ntA

(m)

2

4

6

8

10

08

06

04

02

00

34 68 102 136 1700 Elapsed time (d)

Figure 5 Influence of geocell layer in sand cushion on the settlement of point A

Advances in Civil Engineering 5

about 591 cm when installing two-layer geocell being 190lower than the control case It can be seen that the em-bedment of geocell in sand cushion can effectively reduce thedifferential settlement of the subgrade

43 Influence of Encasement Length of Stone Column on theSubgrade Settlement and Column Lateral DeformationFigure 7 shows the temporal variation of surface settle-ment at the center of the subgrade (point A) with differentencasement length of the stone column In the con-struction stage the settlements increased to 888 cm808 cm 753 cm 707 cm 679 cm 650 cm 628 cm and602 cm with respect to the encasement length of 1D 2D3D 4D 5D 6D 7D and 8D (full encasement) In thepostconstruction stage after 124 days following F3 thesettlements further developed to 1047 cm 961 cm885 cm 820 cm 779 cm 741 cm 708 cm and 679 cmfor the encasement length of 1D 2D 3D 4D 5D 6D 7Dand 8D respectively corresponding to the post-construction settlements of 159 cm 153 cm 132 cm113 cm 100 cm 91 cm 80 cm and 77 cm It is seen thatthe increase of encasement length of the stone columnresults in the reductions of both construction and post-construction settlements of the subgrade It is also ob-served that the settlement decreased more significantlywith the encasement length increasing from 1D to 4Dhowever a further increase of the encasement lengthresulted in a slow decrease of the settlement erefore theencasement length of the stone column up to four times ofthe diameter of the column is found to be adequate in

reducing the settlement based on the consideration ofperformance and economy

Figure 8 shows the differential settlement of the subgradeon day 170 with different encasement length of the stonecolumn When the encasement length was 1D the differ-ential settlement between the center and the edge of sub-grade was about 781 cm If the encasement length increasedto 4D the differential settlement was about 619 cm and thereduction rate was about 207 regarding 1D condition Ifthe encasement length further increased to 8D the differ-ential settlement was about 517 cm corresponding to areduction rate of 338 when compared to 1D condition Itcan be seen that the differential settlement of the subgradegradually decreases significantly with the increase of theencasement length of the stone column

Taking the stone column at the center of the subgrade asan example the lateral deformations of the stone columnwith different encasement lengths are shown in Figure 9elateral deformations were calculated at day 170 that is 124days after the completion of the embankment filling It isobserved that the maximum lateral deformation occurs atthe position of about 2D from the top of the stone columnand it decreases gradually with the increase of encasementlength of the stone column When the encasement length is1D the maximum lateral deformation is about 920 cmWhen the encasement length increases to 4D and 8D themaximum lateral deformation is about 367 cm and 275 cmrespectively corresponding to a reduction rate of 6008and 7008 when compared to 1D condition It is seen thatthe lateral deformation decreased more significantly whenthe encasement length increased from 1D to 4D compared to

Filli

nghe

ight

(m)

Embankment

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Settl

emen

t (m

)

0

2

4

6

10

08

06

04

02

00

5 10 15 20 250Distance from the subgradecenter (m)

Figure 6 Influence of geocell layer in sand cushion on the differential settlement

6 Advances in Civil Engineering

Embankment

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

5 10 15 20 250Distance from the subgradecenter (m)

Filli

nghe

ight

(m)

Settl

emen

t (m

)

12

09

06

03

00

2

4

6

Figure 8 Influence of encasement length on the differential settlement

I3F3I2F2I1F1Construction stage Postconstruction stage

Filli

ng h

eigh

t (m

)

2

4

6

8

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

Settl

emen

t of p

oint

A (m

)

12

09

06

03

00

34 68 102 136 1700Elapsed time (d)

Figure 7 Influence of encasement length on the settlement of point A

Advances in Civil Engineering 7

that from 4D to 8D erefore the encasement length of thestone column up to 4D is found to be adequate in reducingthe lateral deformation of the column when consideringboth the performance and economy

44 Influence of Filling Interval on the Subgrade SettlementFigure 10 shows the temporal variation of surface settlementat the center of the subgrade (point A) with different

standing time between filling stages In the constructionstage the settlement developed rapidly and the excess porewater pressure increased sharply during the filling processand the settlement developed slowly and the excess porewater pressure gradually dissipated in the standing periodIn this stage the settlements developed to 830 cm 836 cm841 cm and 845 cm respectively for the filling intervalextended by 10 days 15 days 20 days and 25 days being

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Settl

emen

t of

poin

t A (m

)

10

08

06

04

02

00

44 88 132 176 2200Elapsed time (d)

Exce

ss p

ore p

ress

ure

of p

oint

A (k

Pa)

7

14

21

28

Filli

ng h

eigh

t (m

)

4

2

0

6

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 10 Influence of filling interval on excess pore water pressure and settlement of point A

Burie

d de

pth

of G

ESC

(m)

1D2D3D4D

5D6D7D8D

60

45

30

15

00

5 10 150Lateral deformation of GESC (cm)

Figure 9 Influence of encasement length on the lateral deformation

8 Advances in Civil Engineering

31 39 45 and 50 larger than the control case Inthe postconstruction stage the settlement further developedto a stable value and the excess pore water pressure graduallydissipated to approximately zero e postconstructionsettlements were 134 cm 130 cm 126 cm and 122 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days being 141 167 196 and218 smaller than the control case It is seen that the ex-tension of the filling interval will promote the consolidationof subgrade soil in the construction stage which results in anincrease in the construction settlement and a reduction inthe postconstruction settlement

Figure 11 shows the differential settlement of the sub-grade with different standing time between filling stagesesettlements were calculated at the time point of 124 daysafter the completion of the embankment filling e dif-ferential settlements between the center and the edge of thesubgrade were about 739 cm 741 cm 744 cm and 745 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days the corresponding increase rateswere about 12 15 19 and 21 when compared tothe control case It can be seen that the extension of thestanding time between filling stages has negligible influenceon the differential settlement of the subgrade

5 Discussion

Composite compression modulus method is one of theavailable methods to compute the settlement of GESCsupported composite foundation and the calculationequation [28] is presented as follows

S 1113944n

i1

Δpi

EcsiHi

Ecs mEps +(1 minus m)Ess

(4)

where S is final settlement of composite foundation Ess iscompression modulus of the soil Eps is compressionmodulus of the column Ecs is composite compressionmodulus of the foundationm is area replacement ratio n arenumbers of calculation layers Hi is thickness of soil layer iDpi is additional stress of soil layer i From the aboveequation the following issues were discussed

(1) e embedment of geocell would provide rein-forcement via the restriction of soil movement andthe concentration of stresses within the geocellhence increasing the stiffness of the sand cushion[29] In addition the confinement provided bygeocells improves the distribution of additionalstress over the subgrade [30] and decreases more atthe center and decreases less at the side [31] As aresult both the center settlement and differentialsettlement on the subgrade surface reduce [30]

(2) e lateral deformation of the stone column de-creased due to the additional confining stress pro-vided by the geogrid encasement and therefore thecompression modulus of the column increases aswell as the composite compression modulus of thefoundation [22 32] As a result the larger the en-casement length of the column the smaller the

Filli

nghe

ight

(m)

Embankment

00 09 18 27 36097

096

095

094

Settl

emen

t (m

)

2

4

6

09

06

03

00

5 10 15 20 250Distance from the subgrade center (m)

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)

Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 11 Influence of filling interval on the differential settlement

Advances in Civil Engineering 9

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

about 591 cm when installing two-layer geocell being 190lower than the control case It can be seen that the em-bedment of geocell in sand cushion can effectively reduce thedifferential settlement of the subgrade

43 Influence of Encasement Length of Stone Column on theSubgrade Settlement and Column Lateral DeformationFigure 7 shows the temporal variation of surface settle-ment at the center of the subgrade (point A) with differentencasement length of the stone column In the con-struction stage the settlements increased to 888 cm808 cm 753 cm 707 cm 679 cm 650 cm 628 cm and602 cm with respect to the encasement length of 1D 2D3D 4D 5D 6D 7D and 8D (full encasement) In thepostconstruction stage after 124 days following F3 thesettlements further developed to 1047 cm 961 cm885 cm 820 cm 779 cm 741 cm 708 cm and 679 cmfor the encasement length of 1D 2D 3D 4D 5D 6D 7Dand 8D respectively corresponding to the post-construction settlements of 159 cm 153 cm 132 cm113 cm 100 cm 91 cm 80 cm and 77 cm It is seen thatthe increase of encasement length of the stone columnresults in the reductions of both construction and post-construction settlements of the subgrade It is also ob-served that the settlement decreased more significantlywith the encasement length increasing from 1D to 4Dhowever a further increase of the encasement lengthresulted in a slow decrease of the settlement erefore theencasement length of the stone column up to four times ofthe diameter of the column is found to be adequate in

reducing the settlement based on the consideration ofperformance and economy

Figure 8 shows the differential settlement of the subgradeon day 170 with different encasement length of the stonecolumn When the encasement length was 1D the differ-ential settlement between the center and the edge of sub-grade was about 781 cm If the encasement length increasedto 4D the differential settlement was about 619 cm and thereduction rate was about 207 regarding 1D condition Ifthe encasement length further increased to 8D the differ-ential settlement was about 517 cm corresponding to areduction rate of 338 when compared to 1D condition Itcan be seen that the differential settlement of the subgradegradually decreases significantly with the increase of theencasement length of the stone column

Taking the stone column at the center of the subgrade asan example the lateral deformations of the stone columnwith different encasement lengths are shown in Figure 9elateral deformations were calculated at day 170 that is 124days after the completion of the embankment filling It isobserved that the maximum lateral deformation occurs atthe position of about 2D from the top of the stone columnand it decreases gradually with the increase of encasementlength of the stone column When the encasement length is1D the maximum lateral deformation is about 920 cmWhen the encasement length increases to 4D and 8D themaximum lateral deformation is about 367 cm and 275 cmrespectively corresponding to a reduction rate of 6008and 7008 when compared to 1D condition It is seen thatthe lateral deformation decreased more significantly whenthe encasement length increased from 1D to 4D compared to

Filli

nghe

ight

(m)

Embankment

No geocell layer (control case)One geocell layer (case 1)Two geocell layers (case 1)

Settl

emen

t (m

)

0

2

4

6

10

08

06

04

02

00

5 10 15 20 250Distance from the subgradecenter (m)

Figure 6 Influence of geocell layer in sand cushion on the differential settlement

6 Advances in Civil Engineering

Embankment

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

5 10 15 20 250Distance from the subgradecenter (m)

Filli

nghe

ight

(m)

Settl

emen

t (m

)

12

09

06

03

00

2

4

6

Figure 8 Influence of encasement length on the differential settlement

I3F3I2F2I1F1Construction stage Postconstruction stage

Filli

ng h

eigh

t (m

)

2

4

6

8

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

Settl

emen

t of p

oint

A (m

)

12

09

06

03

00

34 68 102 136 1700Elapsed time (d)

Figure 7 Influence of encasement length on the settlement of point A

Advances in Civil Engineering 7

that from 4D to 8D erefore the encasement length of thestone column up to 4D is found to be adequate in reducingthe lateral deformation of the column when consideringboth the performance and economy

44 Influence of Filling Interval on the Subgrade SettlementFigure 10 shows the temporal variation of surface settlementat the center of the subgrade (point A) with different

standing time between filling stages In the constructionstage the settlement developed rapidly and the excess porewater pressure increased sharply during the filling processand the settlement developed slowly and the excess porewater pressure gradually dissipated in the standing periodIn this stage the settlements developed to 830 cm 836 cm841 cm and 845 cm respectively for the filling intervalextended by 10 days 15 days 20 days and 25 days being

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Settl

emen

t of

poin

t A (m

)

10

08

06

04

02

00

44 88 132 176 2200Elapsed time (d)

Exce

ss p

ore p

ress

ure

of p

oint

A (k

Pa)

7

14

21

28

Filli

ng h

eigh

t (m

)

4

2

0

6

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 10 Influence of filling interval on excess pore water pressure and settlement of point A

Burie

d de

pth

of G

ESC

(m)

1D2D3D4D

5D6D7D8D

60

45

30

15

00

5 10 150Lateral deformation of GESC (cm)

Figure 9 Influence of encasement length on the lateral deformation

8 Advances in Civil Engineering

31 39 45 and 50 larger than the control case Inthe postconstruction stage the settlement further developedto a stable value and the excess pore water pressure graduallydissipated to approximately zero e postconstructionsettlements were 134 cm 130 cm 126 cm and 122 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days being 141 167 196 and218 smaller than the control case It is seen that the ex-tension of the filling interval will promote the consolidationof subgrade soil in the construction stage which results in anincrease in the construction settlement and a reduction inthe postconstruction settlement

Figure 11 shows the differential settlement of the sub-grade with different standing time between filling stagesesettlements were calculated at the time point of 124 daysafter the completion of the embankment filling e dif-ferential settlements between the center and the edge of thesubgrade were about 739 cm 741 cm 744 cm and 745 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days the corresponding increase rateswere about 12 15 19 and 21 when compared tothe control case It can be seen that the extension of thestanding time between filling stages has negligible influenceon the differential settlement of the subgrade

5 Discussion

Composite compression modulus method is one of theavailable methods to compute the settlement of GESCsupported composite foundation and the calculationequation [28] is presented as follows

S 1113944n

i1

Δpi

EcsiHi

Ecs mEps +(1 minus m)Ess

(4)

where S is final settlement of composite foundation Ess iscompression modulus of the soil Eps is compressionmodulus of the column Ecs is composite compressionmodulus of the foundationm is area replacement ratio n arenumbers of calculation layers Hi is thickness of soil layer iDpi is additional stress of soil layer i From the aboveequation the following issues were discussed

(1) e embedment of geocell would provide rein-forcement via the restriction of soil movement andthe concentration of stresses within the geocellhence increasing the stiffness of the sand cushion[29] In addition the confinement provided bygeocells improves the distribution of additionalstress over the subgrade [30] and decreases more atthe center and decreases less at the side [31] As aresult both the center settlement and differentialsettlement on the subgrade surface reduce [30]

(2) e lateral deformation of the stone column de-creased due to the additional confining stress pro-vided by the geogrid encasement and therefore thecompression modulus of the column increases aswell as the composite compression modulus of thefoundation [22 32] As a result the larger the en-casement length of the column the smaller the

Filli

nghe

ight

(m)

Embankment

00 09 18 27 36097

096

095

094

Settl

emen

t (m

)

2

4

6

09

06

03

00

5 10 15 20 250Distance from the subgrade center (m)

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)

Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 11 Influence of filling interval on the differential settlement

Advances in Civil Engineering 9

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

Embankment

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

5 10 15 20 250Distance from the subgradecenter (m)

Filli

nghe

ight

(m)

Settl

emen

t (m

)

12

09

06

03

00

2

4

6

Figure 8 Influence of encasement length on the differential settlement

I3F3I2F2I1F1Construction stage Postconstruction stage

Filli

ng h

eigh

t (m

)

2

4

6

8

1D (case 2)3D (case 2)5D (case 2)7D (case 2)

2D (control case)4D (case 2)6D (case 2)8D (case 2)

Settl

emen

t of p

oint

A (m

)

12

09

06

03

00

34 68 102 136 1700Elapsed time (d)

Figure 7 Influence of encasement length on the settlement of point A

Advances in Civil Engineering 7

that from 4D to 8D erefore the encasement length of thestone column up to 4D is found to be adequate in reducingthe lateral deformation of the column when consideringboth the performance and economy

44 Influence of Filling Interval on the Subgrade SettlementFigure 10 shows the temporal variation of surface settlementat the center of the subgrade (point A) with different

standing time between filling stages In the constructionstage the settlement developed rapidly and the excess porewater pressure increased sharply during the filling processand the settlement developed slowly and the excess porewater pressure gradually dissipated in the standing periodIn this stage the settlements developed to 830 cm 836 cm841 cm and 845 cm respectively for the filling intervalextended by 10 days 15 days 20 days and 25 days being

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Settl

emen

t of

poin

t A (m

)

10

08

06

04

02

00

44 88 132 176 2200Elapsed time (d)

Exce

ss p

ore p

ress

ure

of p

oint

A (k

Pa)

7

14

21

28

Filli

ng h

eigh

t (m

)

4

2

0

6

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 10 Influence of filling interval on excess pore water pressure and settlement of point A

Burie

d de

pth

of G

ESC

(m)

1D2D3D4D

5D6D7D8D

60

45

30

15

00

5 10 150Lateral deformation of GESC (cm)

Figure 9 Influence of encasement length on the lateral deformation

8 Advances in Civil Engineering

31 39 45 and 50 larger than the control case Inthe postconstruction stage the settlement further developedto a stable value and the excess pore water pressure graduallydissipated to approximately zero e postconstructionsettlements were 134 cm 130 cm 126 cm and 122 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days being 141 167 196 and218 smaller than the control case It is seen that the ex-tension of the filling interval will promote the consolidationof subgrade soil in the construction stage which results in anincrease in the construction settlement and a reduction inthe postconstruction settlement

Figure 11 shows the differential settlement of the sub-grade with different standing time between filling stagesesettlements were calculated at the time point of 124 daysafter the completion of the embankment filling e dif-ferential settlements between the center and the edge of thesubgrade were about 739 cm 741 cm 744 cm and 745 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days the corresponding increase rateswere about 12 15 19 and 21 when compared tothe control case It can be seen that the extension of thestanding time between filling stages has negligible influenceon the differential settlement of the subgrade

5 Discussion

Composite compression modulus method is one of theavailable methods to compute the settlement of GESCsupported composite foundation and the calculationequation [28] is presented as follows

S 1113944n

i1

Δpi

EcsiHi

Ecs mEps +(1 minus m)Ess

(4)

where S is final settlement of composite foundation Ess iscompression modulus of the soil Eps is compressionmodulus of the column Ecs is composite compressionmodulus of the foundationm is area replacement ratio n arenumbers of calculation layers Hi is thickness of soil layer iDpi is additional stress of soil layer i From the aboveequation the following issues were discussed

(1) e embedment of geocell would provide rein-forcement via the restriction of soil movement andthe concentration of stresses within the geocellhence increasing the stiffness of the sand cushion[29] In addition the confinement provided bygeocells improves the distribution of additionalstress over the subgrade [30] and decreases more atthe center and decreases less at the side [31] As aresult both the center settlement and differentialsettlement on the subgrade surface reduce [30]

(2) e lateral deformation of the stone column de-creased due to the additional confining stress pro-vided by the geogrid encasement and therefore thecompression modulus of the column increases aswell as the composite compression modulus of thefoundation [22 32] As a result the larger the en-casement length of the column the smaller the

Filli

nghe

ight

(m)

Embankment

00 09 18 27 36097

096

095

094

Settl

emen

t (m

)

2

4

6

09

06

03

00

5 10 15 20 250Distance from the subgrade center (m)

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)

Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 11 Influence of filling interval on the differential settlement

Advances in Civil Engineering 9

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

that from 4D to 8D erefore the encasement length of thestone column up to 4D is found to be adequate in reducingthe lateral deformation of the column when consideringboth the performance and economy

44 Influence of Filling Interval on the Subgrade SettlementFigure 10 shows the temporal variation of surface settlementat the center of the subgrade (point A) with different

standing time between filling stages In the constructionstage the settlement developed rapidly and the excess porewater pressure increased sharply during the filling processand the settlement developed slowly and the excess porewater pressure gradually dissipated in the standing periodIn this stage the settlements developed to 830 cm 836 cm841 cm and 845 cm respectively for the filling intervalextended by 10 days 15 days 20 days and 25 days being

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Settl

emen

t of

poin

t A (m

)

10

08

06

04

02

00

44 88 132 176 2200Elapsed time (d)

Exce

ss p

ore p

ress

ure

of p

oint

A (k

Pa)

7

14

21

28

Filli

ng h

eigh

t (m

)

4

2

0

6

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 10 Influence of filling interval on excess pore water pressure and settlement of point A

Burie

d de

pth

of G

ESC

(m)

1D2D3D4D

5D6D7D8D

60

45

30

15

00

5 10 150Lateral deformation of GESC (cm)

Figure 9 Influence of encasement length on the lateral deformation

8 Advances in Civil Engineering

31 39 45 and 50 larger than the control case Inthe postconstruction stage the settlement further developedto a stable value and the excess pore water pressure graduallydissipated to approximately zero e postconstructionsettlements were 134 cm 130 cm 126 cm and 122 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days being 141 167 196 and218 smaller than the control case It is seen that the ex-tension of the filling interval will promote the consolidationof subgrade soil in the construction stage which results in anincrease in the construction settlement and a reduction inthe postconstruction settlement

Figure 11 shows the differential settlement of the sub-grade with different standing time between filling stagesesettlements were calculated at the time point of 124 daysafter the completion of the embankment filling e dif-ferential settlements between the center and the edge of thesubgrade were about 739 cm 741 cm 744 cm and 745 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days the corresponding increase rateswere about 12 15 19 and 21 when compared tothe control case It can be seen that the extension of thestanding time between filling stages has negligible influenceon the differential settlement of the subgrade

5 Discussion

Composite compression modulus method is one of theavailable methods to compute the settlement of GESCsupported composite foundation and the calculationequation [28] is presented as follows

S 1113944n

i1

Δpi

EcsiHi

Ecs mEps +(1 minus m)Ess

(4)

where S is final settlement of composite foundation Ess iscompression modulus of the soil Eps is compressionmodulus of the column Ecs is composite compressionmodulus of the foundationm is area replacement ratio n arenumbers of calculation layers Hi is thickness of soil layer iDpi is additional stress of soil layer i From the aboveequation the following issues were discussed

(1) e embedment of geocell would provide rein-forcement via the restriction of soil movement andthe concentration of stresses within the geocellhence increasing the stiffness of the sand cushion[29] In addition the confinement provided bygeocells improves the distribution of additionalstress over the subgrade [30] and decreases more atthe center and decreases less at the side [31] As aresult both the center settlement and differentialsettlement on the subgrade surface reduce [30]

(2) e lateral deformation of the stone column de-creased due to the additional confining stress pro-vided by the geogrid encasement and therefore thecompression modulus of the column increases aswell as the composite compression modulus of thefoundation [22 32] As a result the larger the en-casement length of the column the smaller the

Filli

nghe

ight

(m)

Embankment

00 09 18 27 36097

096

095

094

Settl

emen

t (m

)

2

4

6

09

06

03

00

5 10 15 20 250Distance from the subgrade center (m)

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)

Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 11 Influence of filling interval on the differential settlement

Advances in Civil Engineering 9

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

31 39 45 and 50 larger than the control case Inthe postconstruction stage the settlement further developedto a stable value and the excess pore water pressure graduallydissipated to approximately zero e postconstructionsettlements were 134 cm 130 cm 126 cm and 122 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days being 141 167 196 and218 smaller than the control case It is seen that the ex-tension of the filling interval will promote the consolidationof subgrade soil in the construction stage which results in anincrease in the construction settlement and a reduction inthe postconstruction settlement

Figure 11 shows the differential settlement of the sub-grade with different standing time between filling stagesesettlements were calculated at the time point of 124 daysafter the completion of the embankment filling e dif-ferential settlements between the center and the edge of thesubgrade were about 739 cm 741 cm 744 cm and 745 cmrespectively for the filling interval extended by 10 days 15days 20 days and 25 days the corresponding increase rateswere about 12 15 19 and 21 when compared tothe control case It can be seen that the extension of thestanding time between filling stages has negligible influenceon the differential settlement of the subgrade

5 Discussion

Composite compression modulus method is one of theavailable methods to compute the settlement of GESCsupported composite foundation and the calculationequation [28] is presented as follows

S 1113944n

i1

Δpi

EcsiHi

Ecs mEps +(1 minus m)Ess

(4)

where S is final settlement of composite foundation Ess iscompression modulus of the soil Eps is compressionmodulus of the column Ecs is composite compressionmodulus of the foundationm is area replacement ratio n arenumbers of calculation layers Hi is thickness of soil layer iDpi is additional stress of soil layer i From the aboveequation the following issues were discussed

(1) e embedment of geocell would provide rein-forcement via the restriction of soil movement andthe concentration of stresses within the geocellhence increasing the stiffness of the sand cushion[29] In addition the confinement provided bygeocells improves the distribution of additionalstress over the subgrade [30] and decreases more atthe center and decreases less at the side [31] As aresult both the center settlement and differentialsettlement on the subgrade surface reduce [30]

(2) e lateral deformation of the stone column de-creased due to the additional confining stress pro-vided by the geogrid encasement and therefore thecompression modulus of the column increases aswell as the composite compression modulus of thefoundation [22 32] As a result the larger the en-casement length of the column the smaller the

Filli

nghe

ight

(m)

Embankment

00 09 18 27 36097

096

095

094

Settl

emen

t (m

)

2

4

6

09

06

03

00

5 10 15 20 250Distance from the subgrade center (m)

Filling interval + 0d (control case)Filling interval + 10d (case 3)Filling interval + 15d (case 3)

Filling interval + 20d (case 3)Filling interval + 25d (case 3)

Figure 11 Influence of filling interval on the differential settlement

Advances in Civil Engineering 9

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

construction and post-construction settlements ofthe subgrade However the column encasementcannot significantly affect the embankment pressuredistribution on subgrade surface hence the en-casement length of the column has small influenceon the differential settlement of the subgrade [33]

(3) e extension of standing time between filling stageswould promote the dissipation of the excess porepressure and increase the settlement induced by soilconsolidation in the construction stage As a resultthe compression modulus of soil increases as well asthe composite compression modulus of the foun-dation at the end of the construction stage [1 23]erefore the longer filling interval the larger theconstruction settlement and the smaller the post-construction settlement of the subgrade Howeverthe extension of filling interval cannot affect theadditional stress on the subgrade surface andtherefore it has negligible influence on the differ-ential settlement of the subgrade

6 Conclusions

is study conducted numerical analysis on the settlementbehavior of a soft subgrade reinforced by geogrid-encasedstone column and geocell-embedded sand cushion and themain findings were presented as follows

(1) e simulating settlement was in good agreementwith the field monitoring data which indicates thatthe designed model and adopted parameters arereasonable

(2) e embedment of geocell in sand cushion reducedthe construction settlement the postconstructionsettlement and the differential settlement egeocell embedment will increase the stiffness of sandcushion and therefore adjust the embankmentpressure to distribute more uniformly on subgradesurface

(3) e increase in encasement length of the stonecolumn resulted in the smaller construction settle-ment postconstruction settlement and differentialsettlement e additional confinement provided bythe encasement increases the compression modulusof the column as well as the composite foundatione maximum lateral deformation occurred at theposition of about 2D (two times the column diam-eter) from the top of the stone column and it de-creased more significantly when the encasementlength increased from 1D to 4D compared to thatfrom 4D to 8D e encasement length up to 4D isfound to be adequate in reducing the subgradesettlement and the column lateral deformation basedon the consideration of performance and economy

(4) e extension of the standing time between em-bankment filling stages increased the constructionsettlement due to the promotion of soil consolida-tion while it decreased the postconstruction

settlement However the extension of filling intervalhad little influence on the differential settlement andit would lead to a delay of the embankmentconstruction

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors are very grateful for the financial support of theScience Technology Department of Zhejiang Province(Grant no 2019C03107)

References

[1] M G Bozkurt and D Fratta ldquoDeformation response of softfoundation soils under tall embankmentsmdasha numericalanalysisrdquo in Proceedings of the Geo-Congress 2014 GeorgiaAT USA February 2014

[2] W F V Impe ldquoSoil improvement techniques and theirevolutionrdquo Animal Ence Papers amp Reports vol 20 no 1pp 169ndash178 1989

[3] Q Tang Y Zhang Y Gao and F Gu ldquoUse of cement-chelated solidified municipal solid waste incinerator (MSWI)fly ash for pavement material mechanical and environmentalevaluationsrdquo Canadian Geotechnical Journal vol 54 no 11pp 1553ndash1566 2017

[4] Q Tang F Gu H Chen C Lu and Y Zhang ldquoMechanicalevaluation of bottom ash from municipal solid waste incin-eration used in roadbaserdquo Advances in Civil Engineeringvol 2018 Article ID 5694908 8 pages 2018

[5] Y D Zhou L L Pan Q Tang Y Zhang N Yang and C LuldquoEvaluation of carbonation effects on cement solidifiedcontaminated soil used in road subgraderdquo Advances in Ma-terials Science and Engineering vol 2018 Article ID 527132415 pages 2018

[6] Y C Huang J Chen S J Shi B Li J L Mo and Q TangldquoMechanical properties of municipal solid waste incinerator(MSWI) bottom ash as alternatives of subgrade materialsrdquoAdvances in Civil Engineering vol 2020 Article ID 925451611 pages 2020

[7] S Murugesan and K Rajagopal ldquoGeosynthetic-encased stonecolumns numerical evaluationrdquo Geotextiles and Geo-membranes vol 24 no 6 pp 349ndash358 2006

[8] E R Orekanti and G V Dommaraju ldquoLoad-settlement re-sponse of geotextile encased laterally reinforced granular pilesin expansive soil under compressionrdquo International Journal ofGeosynthetics and Ground Engineering vol 5 no 3 p 172019

[9] J M McKenna W A Eyre and D R WolstenholmeldquoPerformance of an embankment supported by stone columnsin soft groundrdquo Geotechnique vol 25 no 1 pp 51ndash59 1975

[10] S S Gue and Y C Tan ldquoFailures of ground improvementworks in soft groundrdquo Elsevier Geo-Engineering Book Seriesvol 3 pp 665ndash680 2005

10 Advances in Civil Engineering

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11

[11] D A Greenwood ldquoLoad tests on stone columnsrdquo DeepFoundation Improvements Design Construction and TestingASTM West Conshohocken PA USA pp 148ndash171 1991

[12] M Y Fattah and Q G Majeed ldquoA study on the behavior ofgeogrid encased capped stone columns by the finite elementmethodrdquo International Journal of GEOMATE vol 3 no 1pp 343ndash350 2012

[13] M Y Fattah and Q G Majeed ldquoFinite element analysis ofgeogrid encased stone columnsrdquo Geotechnical and GeologicalEngineering vol 30 no 4 pp 713ndash726 2012

[14] M Y Fattah B S Zabar and H A Hassan ldquoSoil archinganalysis in embankments on soft clays reinforced by stonecolumnsrdquo Structural Engineering and Mechanics vol 56no 4 pp 507ndash534 2015

[15] M Y Fattah B S Zabar and H A Hassan ldquoExperimentalanalysis of embankment on ordinary and encased stonecolumnsrdquo International Journal of Geomechanics vol 16no 4 Article ID 04015102 2016

[16] S F Kwa E S Kolosov and M Y Fattah ldquoGround im-provement using stone column construction encased withgeogridrdquo Construction of Unique Buildings and Structuresvol 3 no 66 pp 49ndash59 2018

[17] S N Malarvizhi and K Ilamparuthi ldquoLoad versus settlementof clay bed stabilized with stone and reinforced stone col-umnsrdquo in Proceedings of the 3rd Asian Regional Conference onGeosynthetics Seoul Korea 2004

[18] M Gu M Zhao L Zhang and J Han ldquoEffects of geogridencasement on lateral and vertical deformations of stonecolumns in model testsrdquo Geosynthetics International vol 23no 2 pp 100ndash112 2016

[19] M Hajiazizi and M Nasiri ldquoExperimental and numericalinvestigation of reinforced sand slope using geogird encasedstone columnrdquo Civil Engineering Infrastructures Journalvol 52 no 1 pp 85ndash100 2019

[20] T Ayadat and AM Hanna ldquoEncapsulated stone columns as asoil improvement technique for collapsible soilrdquo Proceedingsof the Institution of Civil EngineersmdashGround Improvementvol 9 no 4 pp 137ndash147 2005

[21] C Yoo and D Lee ldquoPerformance of geogrid-encased stonecolumns in soft ground full-scale load testsrdquo GeosyntheticsInternational vol 19 no 6 pp 480ndash490 2012

[22] S T Kadhim R L Parsons and J Han ldquoree-dimensionalnumerical analysis of individual geotextile-encased sandcolumns with surrounding loose sandrdquo Geotextiles andGeomembranes vol 46 no 6 pp 836ndash847 2018

[23] M S Almeida I Hosseinpour M Riccio and D AlexiewldquoBehavior of geotextile-encased granular columns supportingtest embankment on soft depositrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 141 no 3 Article ID04014116 2015

[24] Z G Zhou Q S Zhang and J L Zheng ldquoAnalysis ofmechanism of improved ground with stone columns rein-forced by geogridsrdquo China Civil Engineering Journal vol 31no 1 pp 21ndash26 1998

[25] C-S Wu and Y-S Hong ldquoLaboratory tests on geosynthetic-encapsulated sand columnsrdquo Geotextiles and Geomembranesvol 27 no 2 pp 107ndash120 2009

[26] G L Madhavi and K Rajagopal ldquoParametric finite elementanalyses of geocell-supported embankmentsrdquo CanadianGeotechnical Journal vol 44 no 8 pp 917ndash927 2007

[27] G L Madhavi ldquoInvestigations on the behaviour of geocellsupported embankmentsrdquo PhD thesis Indian Institute ofTechnology Madras India 2000

[28] Ministry of Housing and Urban Rural Development of thePeoplersquos Republic of China ldquoTechnical code for compositefoundation (GBT50783-2012)rdquo China Planning PressBeijing China 2012

[29] M Y Fattah R R Al-Omari and H A Ali ldquoNumericalsimulation of the treatment of soil swelling using grid geocellcolumnsrdquo Slovak Journal of Civil Engineering vol 23 no 2pp 9ndash18 2015

[30] M Y Fattah W H Hassan and S E Rasheed ldquoEffect ofgeocell reinforcement above buried pipes on surface settle-mentrdquo International Review of Civil Engineering (IRECE)vol 9 no 2 pp 86ndash90 2018

[31] Y F Hao ldquoStudy on the influences of subbase properties onpavement additional stressrdquo Modern Transportation Tech-nology vol 10 no 5 pp 11ndash14 2013

[32] M Ghazavi and J Nazari Afshar ldquoBearing capacity of geo-synthetic encased stone columnsrdquo Geotextiles and Geo-membranes vol 38 pp 26ndash36 2013

[33] H G Kempfert and M Raithel ldquoSoil improvement andfoundation systems with encased columns and reinforcedbearing layersrdquo Elsevier Geo-Engineering Book Series vol 3pp 923ndash946 2005

Advances in Civil Engineering 11