CFG Pile Composite Foundation: Its Engineering ...

Review ArticleCFG Pile Composite Foundation Its Engineering Applicationsand Research Advances

Bantayehu Uba Uge 12 and Yuan-Cheng Guo1

1School of Civil Engineering Zhengzhou University Zhengzhou 450001 China2School of Civil Engineering Hawassa University Hawassa Ethiopia

Correspondence should be addressed to Bantayehu Uba Uge bantayehuugszzueducn

Received 11 August 2020 Revised 15 September 2020 Accepted 15 October 2020 Published 30 October 2020

Academic Editor Huining Xiao

Copyright copy 2020 Bantayehu Uba Uge and Yuan-Cheng Guo +is is an open access article distributed under the CreativeCommons Attribution License which permits unrestricted use distribution and reproduction in any medium provided theoriginal work is properly cited

Problematic soils exist almost everywhere on the globe State-of-the-art solutions tomake civil engineering infrastructures built onthem are still highly sought+e CFG (cement-fly ash-gravel) pile composite foundation system has been widely used in buildingshighways railways and bridge transition sections owing to its proven engineering characteristics in soft ground treatment +ispaper discusses about the development and achievements of its engineering applications along with possible future researchdirections +e remarkable evolution took place in the past to address projectsrsquo strict differential and postconstruction settlementcontrol requirements including embedding the geosynthetic layer into the load transfer platform and combining it with rigidslabs as seen implemented in few CFG pile-supported embankments It was also observed that the interaction of the existing CFGpile composite foundation with an adjacent new foundation pit excavation inevitably presents a complex soil-structure interactionmechanism among the fundamental componentsmdashthe retaining wall mat piles cushion and soil

1 Introduction

Consumption of industrial wastes as dust andor aggregatein geotechnical application is developing globally Cement-fly ash-gravel (CFG) piled composite foundation is a part ofit where the by-product fly ash is used as a constituentmaterial to improve poor engineering properties of soft orweak foundation soils using column technology A CFG pilewith higher bond strength is achieved by mixing cement flyash crushed stone stone chips and sand with water Anincrease in its engineering application has been seen inChina in the last decades with the aim to increase the overallbearing capacity of the natural soft ground and reducepossible uneven settlement of the foundation [1ndash5] Steelreinforcing bars are not usually needed inside the pile andthe industrial waste-fly ash is used as an admixture for theconcrete [6]+e akin column technology commonly used toimprove the soft ground in the USA is termed as ldquorammedaggregate piersrdquo [7] Other internationally practiced verticalsubstructural elements installed to enhance the engineering

behaviour of the soft ground include geosynthetic-encasedstone columns [8] mechanically mixing in situ soil withchemical agent-deepmixed columns (DM) [9 10] and usinghydraulic meansmdashgrouted columns [11] While reviewingthe latest research studies on the CFG pile compositefoundation concepts were also taken from such similar softground improvement technology On the contrary as theword ldquocompositerdquo is conveniently used hereunder asappeared as agreeably by practitioners and researchers in thearea the reader is advised to avoid conflating the nomen-clature with other composites prepared from packagingmaterials such as biodegradable composites So one maylook at the works of several researchers viz listed in [12ndash15]for composites resulting from organic coatings natural fi-bres and biopolymers

Remarkable research works have experimentally ana-lytically and numerically been carried out to comprehendthe mechanism of interaction among the soil pile andsupported structure in the CFG pile composite foundationsystem [16ndash21] Unlike the traditional pile foundation piles

HindawiJournal of EngineeringVolume 2020 Article ID 5343472 26 pageshttpsdoiorg10115520205343472

in the CFG pile composite foundation receive structural loadin an integrated way that involves the contribution of top soilbetween piles +e bearing capacity of the soil between pilesis sufficiently utilised by providing an appropriate thicknessof the mattress layer between the pilesrsquo head and the base ofthe supported structure Because of the stress concentrationon top of piles piles will puncture upward into the cushionlayer (see Figure 1) thus the load is partly transferredthrough negative side friction developing on the upper pilepart After the neutral depth the negative skin friction re-verts into positive +e depth of the neutral plane is mostlylocated above the mid and for the rigid end-bearing pilecomposite foundation it may range from 015 to 035 timesthe pile length [16 22 23] In Figure 1 SS is the totalcompression deformation of the soil between piles δp is thetotal compression deformation of the rigid pile S1 and S2 arethe settlement difference between the top and the bottom ofthe soil layer in the reinforcement area after loading and S3and S4 are the settlement of the pile top and the pile bottomrespectively δ1 and δ2 are the rigid pile head puncture intothe cushion layer and its tip settlement in the underlying soillayer respectively l and l0 are the pile length and the depthof the neutral plane respectively and hc is the thickness ofthe interposed layer

Many authors studied the effect of cushion thickness andits engineering properties on the load redistributionmechanism [24ndash27] Studies indicated that beyond a certainthickness the cushion effectiveness appeared to be quitenegligible Similarly the increase in the cushion thicknessbeyond the optimum depth level had limited influence onthe depth of the neutral surface and pile-soil stress ratio+us for a reasonable and efficient load distribution of pile-soil an appropriate thickness of the cushion layer shall beprovided Experimental and numerical analyses have indi-cated that the pile-soil stress ratio increased as the loadingincreased to a certain level to attain a stable state afterward[23 28 29] One can easily observe from Figure 2 that thepile-soil stress ratio depends on multiple parameters forexample it decreases as the thickness of the cushion layerincreases and gets approximately a constant value at somepoint [23 30ndash32]

+e pile-soil stress ratio is an important reflection pa-rameter for the working condition of the CFG pile compositefoundation Tradigo et al [33] discussed the mechanism ofcushion layer compression during vertical load transmis-sion +ey showed that as the two stiff bodies (pile and raft)approached the cushion from top and bottom plastic strainsdeveloped and spread from the head of the piles Based ondeformation and shear strain contours in the cushion layerRui et al [34] discussed developing a soil-arching phe-nomenon with a multitrapdoor test apparatus and verifiedthe similarity of the slip surface and deformation patternwith that of the diffusion cone model+ey disclosed that thecushionrsquos load redistribution capability depended on theinterposed layer thickness and its properties as well as pilespacing Boussetta et al [35] investigated the cushionthickness effect on the pile-soil stress ratio for a rigid andflexible foundation system +eir study indicated that up toa certain thickness of the mattress layer the efficiency of

rigid inclusion in receiving the applied load increased for therigid foundation compared to embankments (flexiblefoundation) Similar inference has been forwarded withnumerical analyses [36] As piles are practically used in agroup the group effect affected the pile-soil stress ratio[37 38] +e pile spacing as it was somehow related to thearea replacement ratio to be discussed later influenced theload shared by the piles

In order to save investment cost some practitionerscombined various foundation treatment methods to form amixed pile composite foundation consisting of different piletypes andor different lengths of piles +e engineeringpractice of such a new composite foundation exploits thecontribution of the shallow soil strengthened by moreflexible or short piles together with the mobilized bearingcapacity of long piles in the deeper strata [1739ndash43] Tomention some Liu et al [40] and Zhang et al [44] discussedabout piles of different flexibilities Ge et al [45] and Lu et al[46] reported about employing different lengths Hou [47]investigated the vertical force transmission mechanism of arigid long-short pile composite foundation Regardingdissimilar material types Zheng et al [48] conveyed aboutCFG-lime usage and Zhang et al [4] gave attention to CFGpiles used in all parts but rigid concrete piles under the slabedge Zhang and Zhang [49] experimentally studied CFGpiles combined with vibroreplacement stone columns Allthese multipile composite foundations emerged to fulfill theneed for modifying the rigidity and stability of the poorsubsoil as well as drainage requirements to accelerate excesspore water pressure dissipation On top of that it is note-worthy that none is omnipotent by itself but has a certainapplication scope as far as any soft ground treatment methodis concerned

2 Bearing Capacity andSettlement Characteristics

Like any other foundation system CFG pile compositefoundation has to be checked for both its capacity to bearsuperstructural load and its settlement characteristics as theload being transmitted through time So far as the literatureshows the bearing capacity can reasonably be estimated byusing the following equation [50ndash53]

fspk m1Ra1

Ap1+ β1m2

Ra2

Ap2+ β2 1 minus m1 minus m2( 1113857 fsk (1)

where m1 m2 are the replacement rate of the long pile andshort pile respectively β1 β2 are the strength reductioncoefficient of the short pile and soil between piles respec-tively Ra1 Ra2 are the characteristic values of the verticalbearing capacity of the long pile and short pile respectively(see equation (2)) which can be determined according to thestatic load test or the bearing capacity of a single pile de-termined by the strength of the pile body Ap1 Ap2 are thecross-sectional area of the long pile and short pile re-spectively and fspk and fsk are the characteristic values ofthe bearing capacity of the composite foundation and soilbetween piles respectively

2 Journal of Engineering

020100 200 300 400 500 600 700 800 900

022

024

026

028

029

Depth ratio of the neutral plane (Wu et al [23])Pile-soil stress ratio (Wu et al [23] D = 04m L =10m Ec = 40GPa P = 300kPa)Pile-soil stress ratio (Huang [30] D = 05m L = 20m Ec = 120GPa P = 300kPa)Pile-soil stress ratio (Zhang and Shi [31] D = 04m L = 10m Ec = 20GPa P = 400kPa)

Cushion thickness (mm)

Dep

th ra

tio o

f the

neu

tral

pla

ne

0

10

20

30

40

50

Pile

-soi

l stre

ss ra

tio

Figure 2 Cushion thickness vs depth ratio of the neutral plane and pile-soil stress ratio [23 30 31]

S1 δ2

S 2

δ2

Neutralplane

Negativeskin friction

Positiveskin friction

l 0

lh c

S 3S4

External load

From the settlement anddeformation relationshipδp= S3 ndash S2

S1 = S3 + δ1

S4 = S2 ndash δ2

Ss = S1 ndash S4 = δ1 + δ2 + δp

Cushionlayer

Foundation ra

CFG

pile

Toe resistance

Figure 1 Load transfer mechanism and simplified deformation calculation (modified after [22 23])

Journal of Engineering 3

+e characteristic values of the vertical single-pilebearing capacity can be calculated from

Ra12 upi

1113944i

qsili + Apqp (2)

where upiis the perimeter of the pile in the ith soil layer qsi is

the eigenvalue of the pile skin resistance of the ith soil layerqp is the eigenvalue of the pile toe resistance and li is theithlayer soil thickness

According to Yuan et al [53] there existed a differencein the value calculated for Ra according to specifications andthat obtained from the single pile test Reasoning it tohappen because of an increase in the side resistance duringtesting they proposed the enhancement factor to account forthe discrepancy Noticing equation (1) the bearing effectwould also be affected by the area replacement ratio ie thecoverage rate reflecting CFG pilesrsquo area proportion which inturn is affected by the pile diameter and spacing Increasingpile spacing results in a lesser load-sharing ratio between thepile and the soil [37] On the contrary provision of caps atpilesrsquo head increases the replacement ratio and pile-soilstress ratio [37 54] Boussetta et al [35] disclosed that anincrease in the replacement ratio by increasing the pile headdiameter improved the efficiency meanwhile resulting in asettlement reduction up to 50+e centrifuge investigationconducted by Li et al [55] also pointed out reduction in thepile-soil stress ratio as the replacement rate was increased Itcan thus be said that the pile-soil load-sharing ratio is animportant performance indicator as far as the workingmechanism of the CFG pile composite foundation is con-cerned [28 56] +e strength reduction coefficient betweenpile β shows the interaction mechanism between the pile andits surrounding soil As piles are being loaded the shearstrain increases in the vicinity of loaded piles which leads tosoil stiffness nonlinearity and anisotropy Likewise thenatural uneven distribution of the soil layer makes obtaininga single value of β to be unachievable but approximateestimation Moreover for the multipile composite foun-dation the exact value of β that would simultaneously makefull mobilisation of the geotechnical bearing capacity forboth short and long piles is currently unattainable In fact asfar as pile-soil-pile interaction behaviour of the group isconcerned consideration for interactive pile-soil displace-ments remains to be the hottest topic [47 57ndash62]

+e settlement of the composite foundation comprisesthe settlement of both the reinforcement zone and theunderlying soil layer According to the Chinese code fordesign of building foundation GB 50007-2011 the settle-ment calculation can be made using the following equation

S ψsp 1113944

n1

i1

P0

ξEsi

ziαi minus ziminus1αiminus1( 1113857⎡⎣

+ 1113944

n2

in1+1

P0

Esi

ziαi minus ziminus1αiminus1( 1113857⎤⎥⎥⎦

(3)

where ψsp is the empirical settlement calculation coefficientranging between 02 and 10 n1 and n2 are the number of soil

layers in the strengthened area and the rest in the settlementcalculation depth respectively P0 is the additional pressureat the bottom of the basement (kPa) ξ is the increasingcoefficient of compression modulus of the composite soillayer obtained by dividing the characteristic values of thebearing capacity of the composite foundation to those of thenatural foundation Esi is the compression modulus of the ith

soil layer (MPa) zi and ziminus1 are the depth between thebasement bottom and that of theith soil layer and the (i minus 1)th

soil layer (m) respectively and αi and αiminus1 are the averageadditional stress coefficients between the point of calculationon the basement bottom and the bottom surface of the ith soillayer and the (i minus 1)th soil layer respectively

Equation (3) was developed based on isotropic homo-geneous linear deformation theory It is unable to capturethe effect of large loads on the stress-strain behaviour of theadjacent soil in 3D [2 63] Hence a more rigorous theo-retical approach which reflects the soil nonlinear and stresspath-dependent characteristics needs to be developed

Another interesting issue that drawn both practitionersand researchers was postconstruction settlement It hasrecently received growing attention owning to the move indesign focus from bearing capacity to performance re-quirement particularly regarding uneven settlement[64 65] +e difference in the settlement value between thefinal and that at the moment of commencing intended use ofinfrastructures defines the postconstruction settlementwhich can be expressed as

Sgh S minus Se minus St (4)

where Sgh S Se and St are the postconstruction settlementcumulative (final) settlement immediate settlement andconsolidation settlement just at the instant the infrastructurebegins its service respectively

+e common methods used to determine the final set-tlement include the three-point Asaoka and the hyperbolicmethods [66 67] It would become of great importance todevelop procedures that will seize observed settlement datain earlier construction stages to predict postconstructionsettlements andor subsequent construction stages Zhanget al [66] used both the residual primary consolidationsettlement (from the three-point method andor Asaokamethod) and the secondary consolidation settlement (usingthe coefficient of secondary consolidation) to calculate thepostconstruction settlement on a typical soft soil foundationJunjun and Xinghua [65] used the gray system theory forpredicting the postconstruction settlement by improving thebasic model to accommodate for unequal observation timeinterval for settlement observation data from the bridgegroup pile settlement On the contrary Niu et al [63] ap-plied 3D numerical analysis to estimate the total and dif-ferential settlement of the basement raft by crosscheckingthe result with theoretical calculations according to equation(3)

Scholars have also used the shear stress distribution andits range of influence around the pile to predict the com-posite foundation settlement [68 69] As piles are practicallyused in a group based on how close the piles are to each


other there will be a group interaction effect producing anoverlap of stress and displacement field ie the shelteringand reinforcing effect of piles in the group [47 70ndash72] Inorder to reduce the complexity associated with the variationof pile-soil interaction along the pile length the skin frictiondistribution the stiffness difference among the constitutingelements such as the cushion the raft foundation the CFGpile and the soil etc the unit cell reinforcement analysisunder equal stress or equal-strain ideal boundary conditionhas often been chosen by researchers [73 74] +e unit cell(as shown in Figure 3(a)) isolated from the group contains asingle CFG pile surrounded by the soil and acts as a columnwhich may or may not be allowed to deform laterally Whenlateral deformation of the unit cell is considered duringanalysis it results in a lower stress concentration ratio thanthat analysed without allowance for lateral deformation[7 73] However still many researchers prefer to use nu-merical analysis for the settlement investigation of rein-forced soft ground [63 75 76]

3 Engineering Applications

31 Embankments Constructed over Soft Ground CFG pilecomposite foundation has increasingly been implemented inweak soil deposits as column technology either alone [77 78]or combined with (i) geosynthetic reinforcement[19 59 67 79 80] (ii) concrete slabs [4 81] and (iii) othertechnologies such as prefabricated vertical drains [49 82] Ithas been widely employed both in new project routes andwidening existing embankments When an existing pave-ment is widened because of growing traffic demand CFGpiles can be used to support the new added embankment toeliminate pavement distresses due to the differential set-tlement at the overlapping area [83] From experience thestability and performance of the high embankment can bewell improved by embedding the geosynthetic layer into theload transfer platform [84 85] When the CFG piles are usedin conjunction with geosynthetic grids connected to thepilersquos head the load transfer mechanism involves soilarching above the pile caps and the geosynthetic membranebecomes under tension (see Figure 4) [88ndash91] +e soilarching induces shear stresses that are resisted by the tensionmembrane effect of the single geogrid layer or the stiffenedplatform of the multilayer geosynthetic system As a matterof fact soil-arching effect and its practical advantages havebeen well recognized among the geotechnical engineeringsociety since from the time Terzaghi illustrated it with ayielding ldquotrapdoorrdquo it has become more popular whendealing with piles and other geostructures surrounded byeither vertically or laterally moving soil mass [92ndash99]

+e stress concentration ratio (the ratio of column stressto the stress borne by the soil) of piled supported em-bankments without the geosynthetic membrane was re-ported to be lesser than that with geosynthetic reinforcement[100 101] However as reported by some scholars theperformance of the conventional geosynthetic-reinforcedand piled-supported (GRPS) embankments constructedover poor soil deposits has still been shown to have intol-erable uneven settlement relatively larger horizontal

displacement and other instability problems especially inthe face of the stringent high-speed railwaysrsquo requirement[80 102 103] Under such circumstances it is prudent to gofor a relatively rigid slab to eliminate possible differentialsettlement Provision of the slab in the CFG pile-slabstructure (CFGPSS) also addresses the highest concern forthe postconstruction settlement in high-speed railway (HSR)embankments which should be limited under the maximumallowable settlement recommended by standard codes (egChinese Standard TB10001-2016 and British StandardBS8006-1-2010)

Jiang et al [81] presented numerical analysis for theBeijing-Tianjin HSR embankment constructed using theCFGPSS +ey measured and closely monitored thetransverse differential settlement profiles of the slab toexamine the efficiency to meet the stringent post-construction requirements According to their fieldmeasurements a maximum of about 3mm differentialsettlement between the centreline and the toe of theembankment was found throughout the constructionperiod Zhang et al [4 104] also conducted study on theBeijing-Shanghai HSR to examine the effectiveness of theCFGPSS and found a remarkable settlement-controllingeffect

Another potential application area is treating softfoundation soils for embankments constructed in themountainous area When soft soils appear in the mountainarea pavement designers often encounter different engi-neering characteristics than those of ordinary plain softfoundations CFG pile composite foundation is one of themain methods of soft foundation treatment under suchcondition [78]

CFG piles have also been applied to tackle engineeringproblems related with the bump at bridge approaches+is was one of the common challenges attracting re-searchers to investigate abutment piles subjected to lateralsoil movements [105ndash109] A bridge would be unable tooffer its intended service if its approach is prone to dis-continuities resulting from differential settlement of theapproach embankment Xiao et al [110 111] used cen-trifuge model tests and 3D numerical analysis with thefinite difference code FLAC3D to examine the perfor-mance of the CFG-piled bridge approach embankmentwith geosynthetic +eir result indicated the shieldingeffect of CFG piles on the lateral soil displacement and thesettlement of the improved embankment was substantiallyreduced as the CFG pile transferred the load to the deepersoil depth Hence the performance of abutment piles wasevidently improved However beyond the thresholdground replacement ratio (m) of 48 the efficiency ofCFG piles was seen to be limited Li and Bian [112] nu-merically showed using ABAQUS that the dynamic be-haviour of the transition zone at the bridge and theapproach embankment section was improved because ofimplementing CFG piles of varying length It was alsoshown that the amplified dynamic response resultingfrom rail irregularity (track geometry degradations) dueto sudden stiffness variations as the train moves with highspeed was effectively smoothened by employing CFG


piles and the piles neighbouring the bridge had bornehigher dynamic loading when the train passed the tran-sition zone It was also noted that the cushion layer offered

good seismic performance by reducing the dynamic shearwave transmission along with the base isolation system[113 114] Interested reader about the dynamic

Unit cell(equivalent element)

dz

Z

Pile

Ps

Pp

Ps

l0

l

σsz σsz

σsz + dσszσsz + dσsz

τfndash Um

Umτf+

τf+

τfndash

τ

τ

τf

ks

um

Z1

Z2

τ u

Transitionzone

Z ZZ

(I) (II) δb

δt

(a) (b) (c)

(e)

(d)

u

Elasticphase

Plastic phase

Figure 3 Simplified distribution of the pile shaft resistance and relative pile-soil displacement (a) Plane view (b) Elevation view(c) Simplified shaft friction distribution (d) Simplified pile-soil relative displacement (e) Elastic-plastic mechanical property

Surcharge load

Soil arching

Pile cap

Pile

Counter pressurefrom the so oil Steel bar

fixed fulcrum

Firm bearing stratum

Geosynthetic

Figure 4 Typical load transfer mechanism in the fixed geosynthetic-reinforced and pile-supported embankment [86 87]


characteristics of the CFG-piled composite foundationcan also refer to [41 115ndash118]

32 Support for Superstructures +e literature on super-structures overlying on the CFG pile composite foundationis extensive [42 45 50 63 119ndash122] Shen et al [2] statedthat its engineering application in China has begun as asupporting technology for multistorey buildings on the softground and further expanded to a wider range of applica-tions For instance GRPS platforms have also been appliedto control total and uneven settlement for storage tanks[101 123] In fact on a global scale different naming is givento the foundation system somewhat similar to the CFG pilecomposite foundation It comprises ldquorigid inclusionsrdquo[35 36 124] ldquocushioned piled raftsrdquo or ldquopile-enhanced raftsrdquo[27 125] ldquounconnected piled raftsrdquo [126] ldquodisconnectedpiled raftsrdquo [127 128] ldquononcontacted piled raftsrdquo [22 129]ldquorafts on settlement reducing pilesrdquo [130ndash132] and ldquonon-connect piled raftsrdquo [133ndash135] +ese studies have beenconducted numerically and experimentally to describe theload-sharing mechanism of this novel foundation system+e load transmission by provision of a gap filled with acushion between the raft bottom and the pilesrsquo head wasdiscussed in detail+ey all acclaimed the contribution of theinterposed layer in diffusing the applied stress to the pilesand the surrounding soil +e field static test conducted byYang and Liu [136] also confirmed the cushionrsquos capabilityin redistributing the load received from the foundation plateand minimizing the settlement difference between the centreand side areas Saeedi Azizkandi et al [135] in their nu-merical study about the load-sharing mechanism of piles innonconnected piles found that the stiffness of the cushionplayed a great role in transferring a higher portion of thefoundation load to pile heads without significant increase inthe maximum stress developing in the piles

+e application of the CFG pile composite foundation inliquefying soil has shown a reasonable reinforcement effectagainst liquefaction [5 117] It has also been successfullyused in reconstruction projects after an earthquake incident[1] In situations where superstructural inertial force is largein high seismic regions disconnecting piles from the raft hasbeen found to help in reducing the stress concentration atthe pile head [22 125 137] +e resistance to lateral forcesresulting from this and other similar horizontal force-generating events is usually obtained by mobilizing contactfriction along the raftcushion interface [5 114 138] Studieshave shown that the lateral forces and bending moments ofpiles in nonconnected pile rafts are much smaller than thoseof the connected pile [139] It may also be possible topropose geosynthetics to enhance dynamic properties andmodify the resistance to shear strain caused by lateral de-formation [140]

4 Discussion

As is commonly noticed in todayrsquos culture both engineeringattributes and economic issues are crucial when choosingappropriate engineering solution Consequently some may

question how economical the CFG pile composite foun-dation is +e following brief discussion involves the sameand other related engineering perspectives

41 EconomicAppraisal Basically economic factors dependon the construction material and technology deployed at aparticular timemdashas of a device technique or scientific fieldachieved Moreover in the context of green environmentideology environmentally benign geotechnical constructionproject is often associated with resource efficiency and landuse pattern changes [141] Increasing attention is being paidto environmental issues to ensure proper managementstorage andor safe disposal of the huge annual productionof fly ash from power plant combustion andmunicipal wasteincarnation demanding potential application areas forconsumption such as in transportation geotechnics[141 142] +e ability to use such residues as a constituentconstruction material has attracted great attention in thegeotechnical community [143ndash145] +e fly ash in the CFGpile composite foundation is used as an additive and partialcement replacement mixture during concreting In additionto the environmental benefits of using the industrialbyproduct this ldquocarbon-efficientrdquo cementation material willalso affect the plasticity of concrete It influences the con-crete workability bleeding water demand and heat ofhydration It has also been used as aggregate substitutinggravel [146]

At present owing to the maturity of experience andtechnology the project cost and construction period forthe CFG pile composite foundation have been greatlyreduced [1 147] It has also been said that CFG is asustainable emerging construction material [63] Whetherit is implemented in embankment construction or as adisconnected piled raft in building the foundation systemthe load has to be transmitted to the natural ground that ismade competent by the reinforcing effect of the CFG pilesthereby both the soil and piles combine to dissipate theload redistributed through the cushion Suffice to say thatthe CFG pile composite foundation allows the marginalweak underlying soil to participate in transmitting theapplied load in turn contributing to lower project cost [5]When the geomembrane is used as described in precedingsections employing it embraces at least three researchareas related to geosustainability issues viz (1) wastematerial usage (2) sustainable ground improvement and(3) efficient geosynthetics usage Furthermore the con-struction process flow is simple as depicted in Figure 5Once the site setting out is done and the CFG concrete mixis ready hole drilling operation continues to the desiredpile depth and then concreting proceeds After concretepouring is finished to a level above the deign elevation thepile machine mobilizes for the next piling operation Byadjusting the amount and proportion of cement an op-timized CFG pile of strength level between C5 and C25can be achieved

42 Load Transfer Mechanism As discussed elsewhere theload redistribution layer not only ensures the pile and soil


bear the load together but also reduces the stress concen-tration at the bottom of the foundation In order to effec-tively play its role the cushionrsquos frictional characteristic andlayer thickness matter a lot As the frictional characteristicincreases so does the load portion shared by the piles [35]+is is coherent with the reduction of the wage angle as theangle of internal friction increases in Prandtlrsquos failuremechanism which is usually assumed for the stress distri-bution limit at the pile head [150ndash152] If the pile compressesthe cushion layer and continuously penetrates vertically intothe cushion layer as the load increases without forming acontinuous sliding area in the cushion layer then thepunching shear of the cushion layer occurs [153] Regardlessof the cushion material property however an increase in theapplied load will increase the vertical stress received by thepile to a certain level beyond which it will remain more orless constant In the initial loading stage the load bearingcapacity of the soil is mobilized first and then the contri-bution of the pile gradually becomes obvious

Parametric studies conducted by changing the thicknessof the mattress layer indicated that increasing its layer will

reduce the load sharing ratio of the piles +e reflection onthis can start from the condition that the thickness of thecushion layer is zero When structural connection is notallowed under the zero-thickness condition piles will sharemore load while the soil takes very small In other wordswhen the cushion thickness is small the pile-soil stress ratiois relatively large and the bearing capacity of the soil be-tween piles cannot be fully developed +at is due to thestress concentration of the composite foundation the stressat the top of the pile is greater and the stress on the soilbetween the piles is smaller If the thickness is increased anadjustment occurs in such an interaction to increase the loadshared by the soil Nonetheless beyond a certain value nobenefit would be gained by increasing the thickness At thispoint increasing the thickness of the cushion reduces theload borne by rigid piles while increasing the load taken bythe soil between piles which leads to greater plastic de-formation and damage of the soil between piles

Along with the pressure redistribution as piles pierceinto the cushion soil-arching effect appears due to themodulus difference between the pile and the soil It results in

Site levelling andsetting out

Mixing mixture(no supply interruption)

Pile machine atposition

Drilling and sinking the drillpipe to the design depth

Concrete pouring (pumping)and drill pipe withdrawal

Levelling the pile head to a certainheight above its design

elevation (le05m) Move the machine to

the next position

Trimming the extra materialaer the curing period (ge14days)

Pile quality approval andplacing the cushion layer

Figure 5 Construction process flow (modified after [148 149])

Load distributionon GR tensile strip

Pile capSubsoilsupport

Figure 6 Arching in the geosynthetic-reinforced (GR) pile-supported embankment [159]


differential movement to draw more load towards the stifferone +e displacement contours and associated shear strainsbetween adjacent piles form a slip surface patterning either atriangular or an ldquoarchrdquo region depending on the relativecushion thickness and net pile spacing [34 154] Similarinference reported by Zhu and Gong [155] shows that basedon the cushion thickness and pile spacing the archingmechanism progressively develops in the cushion layer whileredistributing the applied load +is phenomenon of soilarching has particularly good achievement prospect in bothconventional and geosynthetic-reinforced CFG-piled em-bankments and remains to be a hot research perspective forfurther study [156ndash158] Nevertheless the current state ofpractice based on numerous analytical numerical and ex-perimental (both field and laboratory) investigations con-firmed the assumption of the concentric arches model to bevalid for a square grid pile arrangement (see Figure 6)[158 160] In the conventional CFG-piled embankments thedeflection of the soil between piles assumes an approxi-mately uniform pattern while the geogrid reinforcement(GR) strips between the piles deflect less than somewhereelse and receive higher load relative to elsewhere

As the arch development follows the proposed con-centric 3D hemisphere illustrated in Figure 6 the connectionmade between the pile and the GR makes the behaviour ofGR pieces along the strip relatively stiffer than those in themiddle +e analysis model usually assumes that the archingmechanism transmits the entire load in two steps and de-composes the load into three vertical components +e firststep deals with the three components of load transferredbecause of the arching effect the portion called ldquoArdquo receivedby the pile (ldquoarchingrdquo) ldquoCrdquo taken by the subsoil and ldquoBrdquo theremainder carried through the geogrids to piles All arevertical loads +e latter two parts are sometimes collectivelytermed as the ldquorestrdquo +e second step is carried out to un-derstand the load-deflection behaviour that implicitly di-vides components B and C In this step while dealing withmembrane action of geotextiles the residual load transferredby the ldquorestrdquo is commonly assumed to be distributed eithertriangularly (eg the German design standardmdashEBGEO2010) or in an equal distribution pattern (eg BritishStandard BS8006) However experimental studies suggestedan inverse triangular distribution with the apex around thepile as depicted in Figure 6 [161 162] As the pile spacingdecreased the vertical stress distribution was found to berelatively uniform between the end and middle of the span[161] Another observation deviating from BS8006 was thatfor both floating and end-bearing piles the tensile force ingeomembranes continued to increase irrespective of thearching height [163] Moreover compared to the unrein-forced case the stress concentration ratio was higher for thegeosynthetic-reinforced case due to the membrane effect[90 101] If floating piles are used instead of end-bearing thestress concentration effect becomes much higher than theeffect of both tension membrane and soil arching [164]

In engineering practice piles are arranged in a squarelayout [2 19 68 80] or triangular pattern [38 146 165 166]When the pilecap configuration is asymmetric the devel-oping soil arching does not follow the 3D hemispherical

dome shape depicted in Figure 6 Rather for instance asillustrated in Figure 7 for piles in the triangular configu-ration having a square pile cap an upper-boundary semi-ellipsoidal shape accompanied by a lower-boundarysemicircular arch would be found In this approach whilethe upper-boundary arch transfers the load onto the pilecaps the other one takes its portion towards the area be-tween adjacent pile caps In order to avoid further problemcomplexity the model developed to obtain Figure 7 excludedconsolidation and creep behaviour pertinent to both soft soiland geosynthetics In the figure s stands for pile spacing anda is the width of the square pile cap thus the gap between theboundary change approximately becomes half of a at the toeand 09 times the clear cap spacing (s-a) at the crown With3D numerical analysis Wijerathna and Liyanapathirana[168] also showed the changes in the arch thickness forcircular piles arranged in a triangular grid but it was foundthat the 3D-dome shape arch above the triangular grid ofcolumns is shorter than the 3D-dome shape arch above thesquare grid

Pile spacing significantly affects the evolution of soilarching In the first place as explained by Roy and Bhasi[90] the arching phenomenon is not instantaneous ratherpropagates from the construction phase to a certain degreeof consolidation before it is fully developed Secondly as thespacing is increased both arching effect and tensioning inthe membrane reduce consequently decreasing the loadtaken by the piles It is then accompanied by an increase inthe stress borne by the foundation soil In the process ofdeveloping the soil arch effect as the relative displacement ofthe pile and soil continues the initial increase in the axialforce along the length of the pile tends to decrease in acertain way after a specific point Associated with this rel-ative movement between the pile and the surrounding soilnegative skin friction (NSF) develops in the upper part of thepile section It is observed that the arching phenomenon andtensionmembrane effect reduce the developing NSF and theNSF developing along the pile affects the performance ofboth geosynthetic-reinforced and conventional-piled rein-forcement [77 90 169] Cao and Zhao [77] found thedistribution of NSF along the length of the end-bearing pilecovered almost the entire length but was distributed in theupper one-third of the length of the floating piles Mean-while as illustrated elsewhere the deformable cushion layerdefuses the foundation load indirectly to the pile creatingNSF on the upper pile body In this regard the NSF de-veloping in the upper pile section becomes a major loadtransfer factor

+e mobilized NSF is mainly governed by the cushionthickness and stiffness of both the cushion and the subsoil[22 135 170] +e greater the compressive modulus of thesoil between the piles the greater the stiffness and the morethe soil shares the overlaying load accordingly the loadcarried by the pile body is relatively reduced +e effect ofsoil compressibility in this regard is well detected boththeoretically and experimentally [23 35 171 172] +e loadapplied on top of the cushion layer generates relative pile-soil displacement large enough to develop shear stressesalong the pile-soil interface As the load increases the pile


compresses the cushion layer and continuously penetratesvertically until the cushion adjusts itself to arrive at a bal-anced state At some specific load level the upward punctureof the pile reverts to downward penetration into the sub-jacent soil In addition due to the difference in stiffness thestress on the pile head becomes higher than that on thesubjacent soil Understanding this phenomenon led manyscholars to envisage that a section existed where both the pileand the surrounding soil underwent equal settlement at thesame depth [56] +e plane at this particular depth is calledas a neutral plane Conveniently an ideal equal-strainboundary condition exists at the neutral plane [7 171 173]For the section above this level the upper pile part settles lessthan the soil in the vicinity +is produces NSF to mobilizealong the shaft However for the depth below that equalsettlement section the lower pile part undergoes greaterrelative settlement than the soil so that positive skin friction(PSF) develops

According to the centrifugal test of Fioravante [64] as theapplied load on the composite foundation of a single rigid pilecontinues the neutral plane moves upward from a depth nearthe middle of the pile Wu et al [23] verified the same andstated that the depth ratio of the neutral surface to the totalpile length assumes a value ranging between 015 and 035 fora pile spacing five times the pilersquos diameter D On the con-trary for pile spacing 4D Dan et al [171] reported the neutralsurface to be located at a depth of 06sim07 l of the pile body+is is consistent to the centrifuge model test result of Wanget al [169] who reported the pile length ratio of 059sim067 fora spacing 4D even though the range of the neutral plane

location is higher than that deduced by Wu et al [23] +iscould be the result of a decrease in the relative pile-subsoildisplacement as the pile length decreases [135] However thestudies gave insight about the effect of pile spacing andreached on the same conclusion that with the increase of pilepacing the depth of the neutral surface moves deeper asshown in Figure 8 +is is because of the group effect As pilesare closely spaced in a group the load carried by each piledecreases and so does the pile-soil stress ratio Subsequentlythe bearing capacity of the pile and the soil between pilescould not be fully developed If the pile spacing is increasedthen the load borne by the individual pile will increase andgradual full play of each pile and the soil between piles wouldbecome apparent Accordingly stress concentration occurson the top of the pile and the relative pile-soil displacementincreases In contrary to this due to arching and tensionmembrane effects in GRPS embankments an increase in thecentre-to-centre pile spacing decreases the neutral planedepth and the NSF also reduces [90]

Another interesting observation which can be madefrom Figure 8 is that the location of the neutral plane staysstable around a particular depth beyond a certain pilespacing In addition to the change in the neutral surfacedepth with time under the working load the literature alsoshows that the maximum NSF befalls on the upper part ofthe piles accompanied by a relatively large pile-soil relativedisplacement [23 29 44 121 169] Saeedi Azizkandi et al[135] numerically indicated the decrease in NSF as thenumber of piles increased +ey also showed that the centralpile experienced the highest amount of NSF compared to the

20

18

16

14

12

10

08

06

04

02

Cap

Cap

Lowerboundary

Upperboundary

135

(s-a

)

05

(s-a

)

Crown 14 (s-a)N

orm

aliz

ed em

bank

men

t hei

ght

(s-a) Y (m)X (m)

ndash25ndash20

ndash15ndash10

ndash050

0510

1520

25 0005

1015

2025

3035

Figure 7 +ree-dimensional soil arching for the triangular pattern pile arrangement [167]


rest in the group Similar result was conveyed by Li et al [55]from their experimental investigation using centrifuge test

Available analytical methods to analyse the pile-soilstress ratio were often developed by assuming the pilemaximum positive and negative frictional stress to eitherfully be mobilized up to the equal settlement section orpartially mobilized in the transition zone around the neutralplane while fully achieved at the pile ends as indicated inFigure 3(c) With the adoption of the first assumption(Figure 3(c)-I) the central elastic zone is neglected tosimplify the calculation in fact based on previous obser-vations that a small amount of relative pile-soil displacementis usually required to mobilize the ultimate shaft frictionvalue which is smaller than 5mm in normal condition[56 174ndash176] In the latter case (Figure 3(c)-II) the plasticstate of the soil developing close to the top and bottom pileends continues in the transition zone depending on therelative soil-to-pile displacement required to fully mobilizefrictional resistance according to equation (5)[23 28 74 177] +en the vertical equilibrium of the in-finitesimal soil element of depth dz is considered taking intoaccount the continuity and boundary conditions so that thecompression deformation compatibility is implemented forthe sections above and below the equal settlement plane toarrive at the expression for solving analytically the pile-soilstress ratio

τ(z) ks wsz minus wpz

11138681113868111386811138681113868

11138681113868111386811138681113868 for 0lewsz minus wpz lt um

τf forwsz minus wpz ge um

⎧⎨

⎩ (5)

where τ(z) is the skin friction along the pile shaft at a depth zks is the initial stiffness gradient of skin friction τf is theultimate pile side friction value wsz is the settlement of thesoil between piles at a depth z wpz is the pile settlement atthe same depthu is the relative pile-soil displacement um isthe critical displacement corresponding to the pile-soildisplacement difference when the pile side friction changes

from the elastic state to the plastic state δt and δb are therelative pile-soil displacement at the pilersquos head and tiprespectively Pp and Ps are the stress borne by the pile andsoil respectively and σsz and σsz + dσsz are the top andbottom stress on the soil slice respectively l and l0 weredefined earlier

+e ultimate pile side friction resistance τf in the plasticstate is related to the shear strength and effective stress of thesoil around the pile which can be calculated as follows

τf c + σ tanϕ c + k0 cz + σs0( 1113857tan ϕ (6)

where k0 tan2(45deg + ϕ0)2 is the passive earth pressurecoefficient of the soil ϕ0 is the internal friction angle of thesoil mass ϕ is the friction angle of pile-soil and σs0 is thevertical stress of the soil surface between piles For cohe-sionless soils equation (6) reverts to τf k0σs0 tanϕ[23 178] It can also be considered that there is no horizontaloffset between the pile and the soil and the calculation iscarried out according to the static earth pressure [171]

Under a combined action of vertical and horizontalloads an increase in lateral load moves the position ofneutral depth upward in the saturated soil medium [179]+is attributes to the greater pile-soil relative settlement asconsolidation continues so the pile body shows severalneutral points With the increase of lateral load the shearband and displacement field of the soil continue to appear inthe direction of load and the friction force between the raftand the cushion increases accordingly As a resultdepending on the cushion thickness the shear force at thepile head decreases and the bending moment at the saidlocation becomes nonnegligible [114 127] Consequentlythe horizontal load is carried by the frictional resistancedeveloping at the contact surface between the cushion andthe raft Judiciously speaking the overall horizontal bearingcapacity is regulated by the minimum lateral resistanceoffered by each foundation part ie the minimum of the

01

02

03

04

05

06

07

Wu et al [23] (D = 04m and l = 10m) Wang et al [169] (D = 04m and l =16m)

Saeedi Azizkandi et al [135] (D = 05m and l = 20m)

Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D

Figure 8 Variation of the neutral plane depth with pile spacing [23 135 170]


lateral bearing capacity of the mat the cushion the interfacebetween the cushion and the raft or the frictional resistancedeveloped at the interface of the cushion and pile-soilground [114] When CFG piles are used to reinforce thenatural ground against liquefaction and as a foundationsystem in seismic regions the cushion provides the samebenefit to the base isolation systems [49 117]

More importantly due to unprecedented populationgrowth and land scarcity in urban dwellings new buildingsare inevitably being built in close proximity with old onessupported by ground improvement technology Under-standing their interaction mechanism is as highly sought asinvestigating the effect of new construction activities onexisting infrastructures found on common foundation typessuch as piles In other words the serviceability of the existingnearby CFG pile composite foundation is also affected byany new tunnelling and deep foundation pit excavation-induced ground deformations While passive loading on theCFG pile composite foundation is implicitly discussed inembankment failure mechanisms (see the failure modesection) the complex interaction of such foundation systemwith their environment as a result of urbanization has gotlittle consideration in previous studies

+e study on the interaction between new excavationand adjacent reinforced composite ground associates con-trolling excavation-induced ground movements to ensuringsafety and stability of structures found on the reinforcedcomposite foundation Causative factors for the incidence ofground movement during excavation was a subject studiedover the past decades [180ndash185] Successful methods havebeen forwarded to decrease the acting force on retainingwalls and consequently their displacement so that nearbystructures and public utilities are protected from damagesrelated to soil movements [186ndash188] It is well known thatthe earth pressure exerted on the earth retaining structureactually depends on the distribution and amount of wallmovement (rigid body translation rotation orand defor-mationdeflection) as a function of the retaining wall typeground condition of the retained mass and applied externalloads of course resulting in a certain amount of associatedground movements [189ndash194] +e following discussion islimited to investigations made on the interaction of theadjacent CFG pile composite foundation with excavationsupported by two different retaining wall typesmdashrigid andcantilever retaining walls

According to the model test results of Wang and Yang[121] when an adjacent excavation work proceeds con-tinuous adjustment of the load borne by CFG piles will occurin a complex way of interaction that is among the pitretaining structure (pit supporting piles) CFG pile com-posite ground and strip of the soil column between pitsupporting piles and the CFG pile composite ground Li et al[119] on their experimental investigation using centrifugetest pointed out that prediction of excavation-induced lateralearth pressure on the retaining wall using the conventionalRankine method was so conservative when the backfill sidewas CFG pile composite ground (see Figure 9) +e bottom-up excavation done on three layers (at 24 32 and 44mdepth progression from top to bottom) was retained by the

pile raft and the composite foundation was set at a distanceof 016 times the depth of excavation Due to the shieldingeffect of CFG piles the reduction of active earth pressure wasprofoundly seen To account the same while using theclassical Rankine theory they considered the change of axialpile load in equation (7) +eir research finding provided animportant direction for improving the economic benefitsgained because of the shielding and reinforcing effect of CFGpiles in design of the adjoining foundation pit-supportingstructure

σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)

where σsz is the vertical stress at a depth z from the pile headpm is the foundation stress As is the bearing area of the soilbetween piles given byAs s2 minus πD24 s is the pile spacingunit weight of the natural foundation soil N is the measuredpile axial load at a depth z and l is the pile length

However current specifications (eg the Chinesetechnical code for support of building foundation pitmdashDBJ41139-2014) for calculating the active earth pressure on theretaining wall for excavation of the foundation pit adjacentto the CFG pile composite foundation conservatively rec-ommend to multiply the characteristic bearing capacity ofthe soil between piles by 12 to obtain an additional load onthe bottom of the cushion and use this value as a surchargewhen the pile end is below the bottom of the foundation pitOtherwise the common stress diffusion method is employedto calculate the additional stress value at the plane positionof the pile tip before applying the Rankine earth pressurecoefficient +is approach does not fully take into accountthe observations about the shielding and reinforcing effect ofCFG piles [29]

Based on the experimental study conducted on the earthpressure evolutionary mechanism against the rigid retainingwall adjoining the rigid composite foundation at 01 timesthe excavation depth (D) Wei [29] also arrived at the sameinference that the additional active earth pressure on theretaining wall is smaller than that of the natural foundationas shown in Figure 9 +e figure compares the works of Wei[29] and Li et al [119] who employed different excavationsupport structures soil properties and distances from theexcavation edge under different surcharge loadings on thecomposite foundation +e work of Li et al [119] simulatedthe process of excavation but only the lateral pressure afterthe final excavation stage was presented here for spacebrevity In addition the lateral pressure predicted accordingto both the traditional Rankine earth pressure theory and theelastic solution for surcharge strip loading [191] is includedas presented by the authors On the left is depicted the labsetup of Wei [29] while the right one roughly represents thescenario of Li et al [119] It can be easily observed that thepresence of vertical reinforcing columns in the compositefoundation made the lateral active pressure acting on theretaining wall to be less than the value obtained usingconventional algorithms +e study of Wei [29] also pointed


out that the shielding effect of the composite foundation wasmore pronounced in the depth range of negative frictiondeveloped along the pile length Somehow after a certaindepth below the neutral plane due to the positive frictionalforce the additional stress on the wall within that depthrange begun to increase approaching to the measured staticearth pressure as the wall rotated about its base (RB) +eincrease in earth pressure at the bottom of the wall is at-tributed to the small displacement that does not allow thefull active state to be reached It is to be reminded that theelastic solution assumes complete active state is achieved Inaddition due to the presence of piles it has been shown thatthe soil sliding surface behind the wall is different from theconventional failure slip surface (see Figure 10)

As the wall moves away from the composite ground inthe translation mode (LT) or rotation around its base (RB)the pile begins to bear additional loads Figure 11 illustratesthe variation of pile head load sharing during wall move-ment Owing to the subsequent movement of the soil as thewall underwent a certain amount of displacement away fromthe reinforced soil the load bearing capacity of the soilbetween the piles decreased and the load shared by the pilescorrespondingly increased

In order to further understand the effect of foundationpit excavation process on the response of nearby CFGpiles the centrifuge experimental work of Li et al [119]was further studied [195 196] +e distribution of axial

load bending moment and deflection of the CFG pileduring each excavation stage at different locations of the6times4 pile group subjected to 180 kPa working load werediscussed but for the sake of space brevity only the axialforce variation is presented here in Figure 12 Figure 12shows the axial force distribution of the monitored CFGpile located at a distance of 12m (ie at the middle of thegroup) behind the 10m deep excavation +e edge of theexcavation was at 20m away from the first row of piles Ascan be seen from the axial force evolution in both loadingprocess and foundation pit excavation stages the increasein the axial force manifested a vertical load transfermechanism with an increasing trend which showed thecontinuation of the increase in the pile-soil stress ratiodue to the process of excavation even though it was notsignificant in the earlier excavation stages In this par-ticular experimental work the reason for the deeperneutral axis was probably the lower coefficient of frictionbetween the pile and the soil which is yet to be verifiedwith future testing Moreover as expected upon the lastexcavation the soil stress relief and lateral displacementbecame greater Consequently the resulting increase inthe overall and relative pile-soil settlement influencedmore the response of the piles closest to excavation thanthe others

According to the numerical analysis of Ren and Qiao[197] an increase in the excavation depth increases the

25

20

15

10

05

00

Li et al [119] (working load 180kPa and distance from excavation - 016D)Rankine Active (working load 180kPa and distance from excavation - 016D)Rankine At Rest (working load 180kPa and distance from excavation - 016D)Wei [29] RB (working load 88kPa and distance from excavation- 01D)Wei [29] LT (working load 88kPa and distance from excavation- 01D)Elastic solution (working load 88kPa and distance from excavation - 01D)Chinese code - JGJ 120-2012 (working load 88kPa and distance from excavation - 01D)

Lateral pressure (kPa)

Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P

Figure 9 Lateral earth pressure distribution along retaining wall depth (modified after Wei [29]-left Li et al [119]-right)


lateral displacement of the CFG piles On the contrary onthe basis of previous research on the conventional pilefoundation under passive load the impact of axial workingload on the lateral pile response is not significant but oncethe serviceability limit is exceeded unperceivable suddenfailure and collapse may occur [198 199] To better ap-prehend this risk in CFG pile composite foundations underworking load further investigation is needed on excavation-induced lateral pile displacement and developing sectionalbending moments

In practice when unexpected project threats appear inthe presence of a wide range of geotechnical design andconstruction uncertainties Peckrsquos observational method(OM) has been proven to be effective in addressing devia-tions from preconstruction behaviour as constructionprogresses [200ndash203] +e OM later amended as

observational modelling uses inverse analysis and soundengineering judgment to recalibrate monitored actualconditions and attack unfavourable ones through ldquopro-gressive modificationrdquo during project implementationwithout compromising safety Yet this model itself has someremaining reticence for its wider use [204]

43 Failure Modes In order to provide theoretical andnumerical solutions to problems regarding stability andintegrity of the foundation system as a whole numerousresearch articles presented implicitly or explicitly the failurepattern analysis For clarity the following briefing is madeseparately on possible failure modes of the cushion pile andpotential failure mechanism in embankments

Wall rotationabout the base

Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation

Retainingwall Coulomb earth

pressure slipsurface

Pile

Foundation

Cushion

P

(b)

Figure 10 Potential failure surface in the soil behind a retaining wall under (a) rotation about its base and (b) translational mode [29]

1200

1300

1400

1500

1600

1700

1800

Average stress of the pile topAverage stress of the soil between piles

Rotation of retaining wall (10‒4rad)

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800

Retaining wall translation (mm)

40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)

Figure 11 Influence of retaining wall movement on the average stress of the soil between piles and the pile head of the compositefoundation under a working vertical load of 88 kPa (a) rotation about the base (b) under the translation mode [29]


431 Failure Mode of the Cushion As previously discussedelsewhere about the load transfer mechanism the pile headpierces into the cushion while the cushion adjusts itself toredistribute the load +is penetration process generateshigh stress concentration and plastic zone developmentpropagating from the side of the pile head as the cushion iscompressed with higher stiffness bodies at its upper andlower boundaries [33] Accordingly depending on thecushion thickness scholars have found that the stress anddisplacement fields resemble an inverted pile on the foun-dation soil +us the failure mode may take three formsoverall shear failure local shear failure and punching shearfailure [151 205] Zhu [206] experimentally examined theeffect of gradation on the slip surface and found the generalshear failure mode for a gravel cushion while local shearfailure for fine gravels having the same cushion thicknessHowever from practical engineering experience undernormal loading condition the thickness of the cushion layeris far less than that required for Terzaghirsquos failure mode tooccur thus the Mandel and Salencon failure mode is usuallyused to theoretically propose design cushion thickness [207]Supporting the same after their numerical analysis Donget al [208] argued that failure mode discussions for thecushion were unnecessary due to the strong bearing capacityit had relative to the weak underlying soil In the concept ofrigid inclusion with the thin load transfer platform the twopossible failure mechanisms in the guidelines of the ASIRIare Prandtlrsquos and punching shear failure modes [152] Underthe cover by rafts or sufficiently thick embankments theultimate limit state consideration prudently satisfies thestress domain to remain within Prandtlrsquos limit state beforeinternal failure of the cushion occurs [209]

432 Failure Mode of the Pile +e failure mechanism forpiles may assumemany possible failure modes depending on

the imposed loads Under vertical loading the pile maycrush bulge fail in bearing at its head andor short floatingpile may undergo punching If piles are subjected to passivehorizontal loading resulting from adjacent excavation orembankment depending on strength diameter and pilelocation either rupture breaking failure (structural failuresdue to shear bending and tensile strains eg [7 127 179])soil flow around the pile pile rotation translation andorcollapse pattern of piles as a whole may occur [210ndash213]Among the cases for passive loading failure under em-bankment loading condition is summarized in the following

433 Failure Mechanism in Embankments Instability ofembankments supported by the CFG pile compositefoundation has been discussed in enormous literaturestudies [78 213ndash215] +e failure pattern normally dependson the strength of the piles and applying the slip-circleanalysis for stability of the improved subgrade needs cau-tions under practical conditions [212 216ndash218] For the CFGpile-net composite foundation Jiang and Wang [147] nu-merically described four failure patterns (viz slip-circleshear failure pile tilting subgrade sliding and soil sliding atthe pile end) based on embankment deformation and subsoillayers +ey implicitly showed that depending on the lo-cation of the pile piles undergone an arc-like deformationwhereby plastic hinge formation occurred in the active zoneas explained by Yapage et al and Broms [212 219] +edeformed piles shaped like concave towards the embank-ment slope under the effect of the geogrid but in the absenceof the geomembrane the arc bulged outwards [214 215]+ecommon failure mode in the latter case was reported to bepile bending and collapse According to Kitazume [218]from the stability point of view under higher-strength pilesthe area replacement ratio has a dominant effect and failureis expected to occur in a collapse failure mechanism

00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P

17871kPaExca-1Exca-2Exca-3

2446kPa4356kPa8225kPa12562kPa15655kPa

Figure 12 Distribution of the monitored axial force during loading and excavation stages [195]


Of the above problems Zheng et al [213] disclosed thatpiles at the centre of the embankment endured smallerbending moment than the others +eir centrifuge test alsodemonstrated that piles may fail with secondary bending inthe upper part depending on the stiffness and embedmentdepth into the stiff layer Dependency on the location of pileswas also observed by other scholars and may lead tocombined failure mechanism [210 217 220] Chen et al[217] recommended an exterior row of columns at the edgeof the slope to provide extra lateral soil resistance to edgepiles For embankments on the inclined soft foundation Guet al [78] experimentally showed the soil deformation andCFG pile fracture to be concentrated in the downhill di-rection see Figure 13 As can be noted from Figure 13 thepile breaks at the interface of the soil layer and the moreapproached to the toe of the slope the greater the degree ofpile fracture and displacement will be

44 Construction Practices and Quality AssuranceAlthough the CFG pile composite foundation has wide ap-plications due to its short construction period and cost-ef-fectiveness undesirable qualities and failure to satisfy qualityrequirements have been encountered during inspections Forexample Hang [221] analysed causes of pile neckingAccording to Teng [222] the construction operation and on-time removal of wastes generated by piling had significantissues on just constructed pile head fractures Ren and Shi [223]reported that the bearing capacity of some CFG piles failed tomeet the design requirement during inspection+us it is very

important to control the quality of CFG piles Being a con-cealed underground work the CFG pile quality shall becontinuously monitored throughout the construction process[224]+e level of contractorrsquos quality management system andsupervisorrsquos quality inspection follow-up plans integrate (1) theworkmanship machinery and technology deployed (2) ef-fective supply chain (3) safety considerations etc which thecontract document entails As the project construction goes onquality assurance reflects a process that is not meant forldquohunting the guiltyrdquo through stringent contractual conditionsbut to assure performance compliance and specification re-quirements are timely met +e construction process basicallystarts off from selecting appropriate construction technologyand the sequence of construction suitable for the field con-dition It has to minimize possible soil disturbance betweenpiles noise and dust pollution during piling To this endmachinery technology is usually deployed through either vi-brating tube-sinking (in silt and cohesive soils) or long spiraldrilling methodmdashbored perfusion cast in situ pile (in clayssilts and dense andmedium sand above the groundwater level)or concrete pumped (for strict pollution control) in which thepiling order may follow continuous or alternate (interval jump)installation sequence [2 5 148]+e piling sequence may affectthe quality of installed piles (squeezing necking or crushingand fracture damages) depending on the type of soil as thepiling proceeds [6]

+e construction process typically follows the flow inFigure 5 After the concrete mix is carried out with theapproved material according to the contract specification

500

400

300

200

100

200 400 600 800 10000

1mm displacement amount

Deformation profile aer test

Sliding surface

Displacement of soil around the pile (red)

Distance from the interior side of the le wall panel (mm)

Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm

) Pretest embankment level

Figure 13 Asymmetrical deformation field and the failure mechanism of the CFG pile-supported embankment on the inclined softfoundation [78]


the concrete is continuously poured into the hole dug to thedesign elevation While concreting in the water-bearingstratum the pile pipe shall not be pulled out immediately inorder to have better concrete quality as well as to avoid pipeplugging +en withdrawal can proceed at a controlledspeed of less than 12mmin preferably 06sim08mmin toprevent pile fracture and hole shrinkage [148 149] Once pileconstruction is finalized field static loading test is carriedout on an inspection batch piled on the same day (the ratio ofthe spot test number to the total pile under considerationbeing 05sim1) after 28 days of curing period based on thelow strain wave velocity and time-history relationship[1 149] Using the low strain dynamic test the supervisorassures the quality of the pile body and its structural integrityas to whether defects exist or not that may affect the bearingcapacity eigenvalue such as pile-end concrete segregationthat reduces the end resistance [223] It is recommended toinstall new piles a week after the old ones [225]

5 Remarks and Future Research Directions

Regardless of how much we know in any field yet there existnew things to explore In the quest to grasp developmenttrends and theoretical research advances to meet the needsof engineering practice it was found that the CFG pilecomposite foundation has addressed both soft ground im-provement and green environment construction issuesNevertheless the following research gaps have been spotted

+e discrepancy between calculated values for thebearing capacity according to code requirements and thosemeasured from field tests still deserves further assessment toaddress questions such as is the difference because of far lessnumber of test piles than calculation piles Or is it due touneven soil distribution encountered while testing Or is itdue to the increase in side resistance while testing Movingon a more rigorous theoretical approach is needed to ac-count for soil nonlinearity and stress path-dependentcharacteristics during settlement predictions Likewise bothstatic and dynamic characteristics of the multipile compositefoundation composed of the CFG pile and other pile typesare not well understood

In the early attempts however little emphasis was givenon the effect of heat disturbance as compared to thefoundation strength and deformation requirement On theone hand the heat exchange performance under alternatingheating condition is sought [226] while on the other handthe behaviour of CFG piles in the permafrost environment isgetting attention [18 227] To better understand the resis-tance to cycles of freezing and thawing process further studyis needed

For adjacent excavation activities the load transfermechanism and excavation-induced settlement can furtherbe explored through parametric studies by varying somefactors such as excavation supporting system stiffness theprocess of excavation distance from the excavation theformation level relative to the CFG pile toe the pattern ofsoil movement (magnitude and distribution profile) alongthe depth interpose layer characteristics and thicknessengineering properties and drainage condition of the

retained soil pilesrsquo arrangement and spacing pile lengthconsidering hybrid piles (various types and dimensions)replacement ratio and working load Moreover from theprobabilistic analysis point of view its behaviour undercomplex geological conditions is still unclear [21] In orderto capture the soil-structure interaction while simulating theexcavation process using model tests adopting advancedtechnologies to directly measure the response of eachcomponent during the experiment is essentially soughtnonetheless in the current experimental setup consider-ation to account for factors such as superstructural stiffnessand the influence of retaining wall installation during soilfilling still lags behind perfection [228ndash230]

Another increasing interest lays on issues with GRPSembankments One issue is the soil-arching phenomenon Itwas found that themodern 2D trapdoor test needs validationwith 3D or field tests [231] Along with it the influence oftrapdoorrsquos rigidity and shape on arching is yet to be ex-plored +e same goes regarding the influence of loadingcondition (uniform localized or cyclic and seismic) on soilarching On the contrary it certainly becomes noteworthy topromote studying the complex construction processes andlong-term performance such as creep and stress recovery

In addition future study may be needed regarding thefailure mechanism of CFG piles under the combined failuremode +is may be required in order to resolve the questionabout how gradually or suddenly the failure of piles de-velops whether it happens simultaneously or not to all pilesand the specific cause of the pile fracture caused by tensionbending or shearing

6 Conclusions

+e paper looks back over the development and engineeringapplications of the CFG pile composite foundation Eventhough more concentration was made on the load transfermechanism sections were devoted to its economic appraisalpossible failure mechanism construction practices andquality assurances during inspections +e findings aresummarized as follows

For superstructures supported by the CFG pile com-posite foundation the key engineering achievement was tobring marginalized natural soft ground into full play insupporting foundation loads +e deformable load distri-bution layer between the raft and the pile generates highnonlinearity in the system and hence creates a complexload-sharing phenomenon to make the pile and soil worktogether and adjust the pile-soil stress ratio +e cushionthickness frictional characteristics and stiffness likelycontrol the load transferred to piles through the head andnegative shaft friction +e neutral depth location is de-pendent on but not limited to the subsoil stiffness thecushion properties and thickness the pile spacing pilelength replacement ratio and location of the pile in thegroup +ese parameters in turn affect the pile-soil stressratio

In practice CFG pile composite foundation will bear notonly vertical pressures but also horizontal loads When theyare subjected to horizontal loading their lateral bearing


capacity is normally obtained from the frictional shearingresistance mobilized between the mat and the interposedlayer However judicious assessment may be necessary tocheck whether or not the lateral ultimate bearing capacity ofeach part is exceeded Even though the shear force at the pileheads was found to decrease as the cushion thickness in-creases the frictional resistance developed at the interface ofthe cushion and pile-soil ground may control the overalllateral capacity if it is less than the lateral resistance offeredby the lateral bearing capacity of the mat the cushion or theinterface between the cushion and the raft When CFG pilesare subjected to passive loading from adjacent excavation-induced ground movements a complex interaction arisesamong the excavation supporting structure and the existingcomposite foundation +e excavation activity just addscomplexity to the already intricate soil-structure interactionproblem as the foundation continuously adjusts the pile-soilstress ratio Moving on both the active lateral earth pressureexerted on the retaining wall and the failure surface for thenatural soil between piles differ from the conventional so-lution Albeit indoor tests with advanced technologies whichare capable of directly measuring the response of constituentstructural elements could be used to simulate the excavationprocess and the current experimental setup still lags behindperfection to consider factors such as superstructural stiff-ness and the influence of retaining wall installation duringsoil filling +us full understanding of the behaviour underpassive loading remains to be an opportunity for furtherinvestigations

For embankments constructed over CFG pile-reinforcedsubgrade soil due to stiffness differences arching phe-nomenon develops and piles attract larger load proportionwhereas the natural ground bears approximately uniformpressure distribution +e major portion of the load istransferred through arching When geosynthetic rein-forcement is included strips of geomembranes between pilesbecome stiffer than those in the middle +is allows thereinforcement strips to receive a larger portion of the loadthan elsewhere with an inverse triangular distributionpattern Depending on the pile configuration the developingarch may establish a concentric 3D hemispherical domeshape or semiellipsoidal upper boundary accompanied by asemicircular lower-boundary arch Arching phenomenon isnot instantaneous but develops fully after a certain amountof consolidation Compared to the apparent load transfermechanism through cushions under rigid structural ele-ments the load transferred through negative friction inGRPS embankments is lesser due to arching and membraneeffect In this regard further research is needed to under-stand the time effect of soil-arching development the in-fluence of the construction process the effect of the localizedload distribution and cyclic loading on soil arching Yet tobe given further consideration is the long-term performanceof geosynthetic-reinforced CFG-piled embankments

As far as the failure mode in an isolated CFG pile isconcerned it is found that crushing bulging shear andorpunching would occur on the top part of the pile+e qualityof the upper pile body is affected by the method and se-quence of construction Consequently close on-site

operational assessment and continuous quality inspectionsare needed throughout the process of construction +ethickness of the cushion layer and the nature of the foun-dation above it determine the apparent failure mechanismdeveloping in the load transfer platform For a relativelythick cushion beneath the rigid foundation (such as mat orslabs on grade) Prandtlrsquos failure mechanism takes place Ifthe cushion is covered by the flexible foundation (such asthin embankments) then punching shear failure modedevelops For a group of piles pile bending and collapse wereidentified as common failure modes for internal stability inembankments supported by the CFG pile compositefoundation However depending on the stiffness of firmstratum area replacement ratio stiffness and location of thepiles pile spacing height of the embankment and incli-nation of the soft ground bottom a combined failure en-velopemay trigger From a practical point of view numericalanalysis is usually employed to check stability and potentialfailure mechanisms

Conflicts of Interest

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

Acknowledgments

+e authors gratefully acknowledge the support ofZhengzhou Universityʼs Presidential Scholarship Programfor sponsoring the research area ldquoFoundation Treatment andFoundation Pit Support Engineeringrdquo

References

[1] J Chen W Chen K Zhang and L Li ldquo+e application ofCFG pile composite foundation in the reconstruction of theDujiangyanrdquo IOP Conference Series Earth and Environ-mental Science vol 300 Article ID 022159 2019

[2] Q Shen L Liu and J Yuan ldquoStudy on design and engi-neering application of CFG pile composite foundationrdquo BolTec vol 55 pp 24ndash33 2017

[3] X Shuo and W Yunxia ldquoResearch progress and develop-ment of CFG pile composite foundationrdquo Applied Mechanicsand Materials vol 353ndash356 pp 706ndash710 2013

[4] D Zhang Y Zhang C W Kim et al ldquoEffectiveness of CFGpile-slab structure on soft soil for supporting high-speedrailway embankmentrdquo Soils and Foundations vol 58 no 6pp 1458ndash1475 2018

[5] Z Zhao B L Hallanger Z Shi et al ldquoDesign discussion andconstruction quality management of CFG pilerdquo Interna-tional Journal of Services Sciences vol 5 pp 529ndash536 2013

[6] S Li B Yan H An et al ldquoCauses and processing methodsfor quality defects of soft foundation reinforcement usingCFG pilesrdquo Chinese Journal of Geotechnical Engineeringvol 39 pp 216ndash219 2017

[7] J Han ldquoRecent research and development of ground columntechnologiesrdquo Proceedings of the Institution of Civil Engi-neers-Ground Improvement vol 168 no 4 pp 246ndash2642015

[8] J Castro and C Sagaseta ldquoDeformation and consolidationaround encased stone columnsrdquo Geotextiles and Geo-membranes vol 29 no 3 pp 268ndash276 2011


[9] P Jamsawang D Bergado A Bandari and P VoottipruexldquoInvestigation and simulation of behavior of stiffened deepcement mixing (SDCM) pilesrdquo International Journal ofGeotechnical Engineering vol 2 no 3 pp 229ndash246 2008

[10] S-L Shen J Han and Y-J Du ldquoDeep mixing inducedproperty changes in surrounding sensitive marine claysrdquoJournal of Geotechnical and Geoenvironmental Engineeringvol 134 no 6 pp 845ndash854 2008

[11] C J Serridge and O Synac ldquoGround improvement solutionsfor motorway widening schemes and new highway em-bankment construction over soft groundrdquo Proceedings of theInstitution of Civil Engineers-Ground Improvement vol 11no 4 pp 219ndash228 2007

[12] H-Y Jeon ldquoGeotextile composites having multiple func-tionsrdquo in GeotextilesElsevier Amsterdam Netherlands2016

[13] Z Song H Xiao and Y Zhao ldquoHydrophobic-modifiednano-cellulose fiberPLA biodegradable composites forlowering water vapor transmission rate (WVTR) of paperrdquoCarbohydrate Polymers vol 111 pp 442ndash448 2014

[14] H Huang L Mao Z Li et al ldquoMultifunctional polypyrrole-silver coated layered double hydroxides embedded into abiodegradable polymer matrix for enhanced antibacterialand gas barrier propertiesrdquo Journal of Bioresources andBioproducts vol 4 pp 231ndash241 2019

[15] M Daria L Krzysztof and M Jakub ldquoCharacteristics ofbiodegradable textiles used in environmental engineering acomprehensive reviewrdquo Journal of Cleaner Productionvol 268 Article ID 122129 2020

[16] W Jiang and Y Liu ldquoDetermination of neutral plane depthand pile-soil stress ratio of the rigid pile composite foun-dationrdquo Rock and Soil Mechanics vol 39 pp 4554ndash45602018

[17] F-Y Liang L-Z Chen and X-G Shi ldquoNumerical analysisof composite piled raft with cushion subjected to verticalloadrdquo Computers and Geotechnics vol 30 no 6pp 443ndash453 2003

[18] J Liu and Y Jia ldquoTemperature analysis of CFG pile com-posite foundation in high latitudes and low altitude islandpermafrostrdquo International Journal of Structural Integrityvol 10 no 1 pp 85ndash101 2019 httpsdoiorg101108IJSI-07-2018-0045

[19] Y Shen and H Wang ldquoOptimization design on CFG-pilefoundation with different cushion thickness in beijing-shanghai high-speed railwayrdquo Transportation InfrastructureGeotechnology vol 3 no 1 pp 3ndash20 2016 httpsdoiorg101007s40515-015-0026-7

[20] Q Teng X Yao S Li and J Guan ldquoFinite element analysisof bearing capacity on the composite foundation of grouppilerdquo IOP Conference Series Earth and Environmental Sci-ence vol 304 2019 httpsdoiorg1010881755-13153043032061 Article ID 032061

[21] X Z Wu and J-X Xin ldquoProbabilistic analysis of site-specificload-displacement behaviour of cement-fly ash-gravel pilesrdquoSoils and Foundations vol 59 no 5 pp 1613ndash1630 2019httpsdoiorg101016jsandf201907003

[22] V Fioravante and D Giretti ldquoContact versus noncontactpiled raft foundationsrdquo Canadian Geotechnical Journalvol 47 no 11 pp 1271ndash1287 2010 httpsdoiorg101139T10-021

[23] C Wu W Guo and Y Li ldquoCalculation of neutral surfacedepth and pile-soil stress ratio of rigid pile compositefoundation considering influence of negative frictionrdquo

Chinese Journal of Geotechnical Engineering vol 38pp 278ndash287 2016

[24] H Chen and Y Li ldquoExperimental study on load transfer lawof rigid pile-raft composite foundationsrdquo Modelling Mea-surement and Control C vol 78 no 2 pp 225ndash241 2017

[25] A T Ghalesari and H Rasouli ldquoEffect of gravel layer on thebehavior of piled raft foundationsrdquo in Advances in SoilDynamics and Foundation EngineeringAmerican Society ofCivil Engineers Shanghai China 2014

[26] H Rasouli A Taghavi Ghalesari M Modarresi andA Hasanzadeh ldquoNumerical study of non-contact piled raftinteraction under static loadsrdquo in Civil Engineering andUrban PlanningWorld Scientific Xirsquoan China 2017

[27] V J Sharma S A Vasanvala and C H Solanki ldquoBehaviourof load-bearing components of a cushioned composite piledraft foundation under axial loadingrdquo Slovak Journal of CivilEngineering vol 22 no 4 pp 25ndash34 2014

[28] L Miao F Wang and W Lv ldquoA simplified calculationmethod for stress concentration ratio of composite foun-dation with rigid pilesrdquo KSCE Journal of Civil Engineeringvol 22 no 1 pp 1ndash8 2018

[29] Y Wei Research on evolutionary mechanisms and calcula-tion method of earth pressure against rigid retaining wallsclose to rigid composite foundation PhD DissertationZhengzhou University Zhengzhou China 2018

[30] S G Huang ldquoStudy on the bearing behavior of CFGcomposite foundationrdquo in Rock Mechanics Achievementsand Ambitions M Cai Ed Taylor amp Francis GroupLondon UK 2012

[31] H Zhang and M L Shi ldquoMechanical performance of set-tlement-reducing pile foundation with cushionrdquo AdvancedMaterials Research vol 368ndash373 pp 2545ndash2549 2011httpsdoiorg104028wwwscientificnetAMR368-3732545

[32] J Lai H Liu J Qiu et al ldquoStress analysis of CFG pilecomposite foundation in consolidating saturated minetailings damrdquo Advances in Materials Science and Engi-neering vol 2016 Article ID 3948754 12 pages 2016

[33] F Tradigo F Pisano and C di Prisco ldquoOn the use ofembedded pile elements for the numerical analysis of dis-connected piled raftsrdquo Computers and Geotechnics vol 72pp 89ndash99 2016

[34] R Rui J Han Y Ye et al ldquoLoad transfer mechanisms ofgranular cushion between column foundation and rigidraftrdquo International Journal of Geomechanics vol 20 ArticleID 04019139 2020

[35] S Boussetta M Bouassida A Dinh J Canou and J DuplaldquoPhysical modeling of load transfer in reinforced soil by rigidinclusionsrdquo International Journal of Geotechnical Engi-neering vol 6 no 3 pp 331ndash342 2012

[36] S Boussetta M Bouassida and M Zouabi ldquoAssessment ofobserved behavior of soil reinforced by rigid inclusionsrdquoInnovative Infrastructure Solutions vol 1 p 27 2016

[37] P Bui Q Luo L Zhang and M Zhang ldquoGeotechnicalcentrifuge experiment model on analysis of pile-soil loadshare ratio on composite foundation of high strength con-crete pilerdquo in Proceedings of the International Conference onTransportation Engineering pp 3465ndash3470 American So-ciety of Civil Engineers Southwest Jiaotong UniversityChengdu China 2009

[38] Y Li D Zhang and C Wu ldquoSensitivity study of the bearingcapacity and pile-soil stress ratio for aeolian sand foundationtreated with CFG pilesrdquo Revista Tecnica de la Facultad deIngenierıa Universidad del Zulia vol 39 pp 124ndash135 2017


[39] Y Gao H M Li and J L Yao ldquoDesign research andtechnical application of the multi-type-pile compositefoundationrdquo Applied Mechanics and Materials vol 170ndash173pp 110ndash114 2012 httpsdoiorg104028wwwscientificnetAMM170-173110

[40] K Liu X Xie and H Liu ldquoPerformance of rigid-flexible-pilefoundation with cushionrdquo Proceedings of the Institution ofCivil Engineers-Geotechnical Engineering vol 163 no 4pp 221ndash227 2010 httpsdoiorg101680geng20101634221

[41] V J Sharma S A Vasanvala and C H Solanki ldquoStudy ofcushioned composite piled raft foundation behaviour underseismic forcesrdquo Australian Journal of Civil Engineeringvol 13 no 1 pp 32ndash39 2015 httpsdoiorg1010801448835320151092636

[42] R Song L Lang and J Wang ldquoApplication of long-short-pile composite foundation of high-rise building in soft soilrdquoApplied Mechanics and Materials vol 256ndash259 pp 57ndash602013

[43] J-J Zheng S W Abusharar and X-Z Wang ldquo+ree-di-mensional nonlinear finite element modeling of compositefoundation formed by CFG-lime pilesrdquo Computers andGeotechnics vol 35 no 4 pp 637ndash643 2008 httpsdoiorg101016jcompgeo200710002

[44] E Zhang L Yu and X He ldquoAnalysis of action mechanismfor rigid flexible pile composite foundationrdquo Revista Tecnicade la Facultad de Ingenierıa Universidad del Zulia vol 39no 11 pp 260ndash270 2016

[45] X Ge B Li and Z Hu ldquoApplication and analysis of long-short-pile composite foundation of high-rise building in softsoilrdquo Build Structure vol 39 pp 114ndash116 2009

[46] H Lu Q Gao B Zhou et al ldquoExperimental research onbearing capacity of long-and-short pile composite founda-tionrdquo Chinese Journal of Underground Space and Engi-neering vol 11 pp 56ndash63 2015

[47] S Hou Research on force transmission mechanism and designtheory of rigid long-short pile composite foundation PhDDissertation Zhengzhou University Zhengzhou China2020

[48] J-J Zheng S W Abusharar and C He ldquoDesign theory andapplication of CFG-lime pile composite groundrdquo in Pro-ceedings of the 6th International Conference on GroundImprovement Techniques Coimbra Portugal 2005

[49] M Zhang and X Zhang ldquoA field experimental study ofcomposite foundation with CFG pile + vibro-replacementstone column pile in liquefaction areardquo in Proceedings of the2017 2nd International Symposium on Advances in ElectricalElectronics and Computer Engineering (ISAEECE 2017)Atlantis Press Guangzhou China 2017

[50] Q-n Chen M-h Zhao G-h Zhou and Z-h ZhangldquoBearing capacity and mechanical behavior of CFG pilecomposite foundationrdquo Journal of Central South Universityof Technology vol 15 no S2 pp 45ndash49 2008 httpsdoiorg101007s11771minus008minus0434minus8

[51] S-H Ye and X-N Gong ldquoStatic load test of a project CFGpile composite foundationrdquo Mechanics and ArchitecturalDesign pp 175ndash180 2016

[52] F Yan and X Huang ldquoExperiment research of bearingbehavior on lime-soil pile and CFG pile rigid-flexible pilecomposite subgraderdquo in Ground Improvement and Geo-syntheticsAmerican Society of Civil Engineers ShanghaiChina 2014

[53] L Yuan Z Keneng L Chuang and H Jie ldquoTest on en-hancement coefficient of lateral resistance about CFG micro

pilerdquo Journal of Central South University of Technologyvol 48 2017

[54] V D Tran J-J Richard and T Hoang ldquoSoft soil im-provement using rigid inclusions toward an application fortransport infrastructure construction in Vietnamrdquo in NewProspects in Geotechnical Engineering Aspects of Civil In-frastructures H Khabbaz H Youn and M Bouassida EdsSpringer International Publishing Cham Switzerland 2019

[55] L Li J Huang Q Fu et al ldquoCentrifuge experimental studyof mechanical properties of composite foundation withdifferent replacement rates under additional loadrdquo Rock andSoil Mechanics vol 38 pp 131ndash139 2017

[56] M Zhao Q Chen and L Zhang ldquoCalculation of pile-soilstress ratio of rigid pile composite foundation with con-sideration of upward penetration of pilesrdquo Journal ofHighway and Transportation Research and Development(English Edition) vol 5 no 1 pp 1ndash6 2011 httpsdoiorg101061JHTRCQ0000033

[57] M Cao and A Zhou ldquoAnalytical solutions to interactionfactors of two unequal length piles under horizontal loadsrdquoInternational Journal of Geomechanics vol 19 2019 httpsdoiorg101061(ASCE)GM1943-56220001369 Article ID06019003

[58] W Liu X Yang S Zhang X Kong and W Chen ldquoAnalysisof deformation characteristics of long-short pile compositefoundation in salt lake area Iranrdquo Advances in Civil Engi-neering vol 201915 pages 2019 httpsdoiorg10115520195976540 Article ID 5976540

[59] W Liu S Qu H Zhang and Z Nie ldquoAn integrated methodfor analyzing load transfer in geosynthetic-reinforced andpile-supported embankmentrdquo KSCE Journal of Civil Engi-neering vol 21 no 3 pp 687ndash702 2017 httpsdoiorg101007s12205-016-0605-3

[60] B B Sheil B A McCabe E M Comodromos andB M Lehane ldquoPile groups under axial loading an appraisalof simplified non-linear prediction modelsrdquo Geotechniquevol 69 no 7 pp 565ndash579 2019 httpsdoiorg101680jgeot17R040

[61] A D Wang W D Wang M S Huang J B Wu B B Sheiland B A McCabe ldquoDiscussion interaction factor for largepile groupsrdquo Geotechnique Letters vol 6 no 3 pp 234ndash2402016 httpsdoiorg101680jgele1600082

[62] S C Wong and H G Poulos ldquoApproximate pile-to-pileinteraction factors between two dissimilar pilesrdquo Computersand Geotechnics vol 32 no 8 pp 613ndash618 2005 httpsdoiorg101016jcompgeo200511001

[63] X Niu Y Yao Y Sun Y He and H Zhang ldquo3D numericalanalysis of synergetic interaction between high-rise buildingbasement and CFG piles foundationrdquo Applied Sciencesvol 8 no 11 p 2040 2018 httpsdoiorg103390app8112040

[64] V Fioravante ldquoLoad transfer from a raft to a pile with aninterposed layerrdquo Geotechnique vol 61 no 2 pp 121ndash1322011 httpsdoiorg101680geot700187

[65] C Junjun and W Xinghua ldquoPost-construction settlementcalculation and prediction for group piles foundation of highspeed railway bridgerdquo Advances in Natural SciencesNanoscience and Nanotechnology vol 8 pp 1ndash7 2016httpsdoiorg1039687978

[66] M Zhang J J Li and C H K Qin ldquoAnalysis and discussionon post-construction settlement of soft soil foundationtreatment test section of highwayrdquo IOP Conference SeriesEarth and Environmental Science vol 81 2017 httpsdoiorg1010881755-1315811012151 Article ID 012151


[67] G Zheng Y Jiang J Han and Y-F Liu ldquoPerformance ofcement-fly ash-gravel pile-supported high-speed railwayembankments over soft marine clayrdquoMarine Georesources ampGeotechnology vol 29 no 2 pp 145ndash161 2011 httpsdoiorg1010801064119X2010532700

[68] Z-F Wang W-C Cheng Y-Q Wang and J-Q DuldquoSimple method to pridict settlement of composite foun-dation under embankmentrdquo International Journal of Geo-mechanics vol 18 2018 httpsdoiorg101061(ASCE)GM1943-56220001293 Article ID 04018158

[69] M-h Zhao L Zhang and M-h Yang ldquoSettlement calcu-lation for long-short composite piled raft foundationrdquoJournal of Central South University of Technology vol 13no 6 pp 749ndash754 2006 httpsdoiorg101007s11771minus006minus0026minus4

[70] S-H Lee and C-K Chung ldquoAn experimental study of theinteraction of vertically loaded pile groups in sandrdquo Ca-nadian Geotechnical Journal vol 42 no 5 pp 1485ndash14932005 httpsdoiorg101139t05-068

[71] H G Poulos and E H Davis Pile Foundation Analysis andDesign John Wiley amp Sons New York NY USA 1980

[72] A D Wang W D Wang M S Huang and J B WuldquoInteraction factor for large pile groupsrdquo GeotechniqueLetters vol 6 no 1 pp 58ndash65 2016 httpsdoiorg101680jgele1500139

[73] J Castro and C Sagaseta ldquoConsolidation and deformationaround stone columns numerical evaluation of analyticalsolutionsrdquo Computers and Geotechnics vol 38 no 3pp 354ndash362 2011 httpsdoiorg101016jcompgeo201012006

[74] Q Luo and Q Lu ldquoSettlement calculation of rigid pilecomposite foundation considering pile-soil relative slipunder embankment loadrdquo China Journal of Highway andTransport vol 31 pp 20ndash30 2018

[75] M Khabbazian V N Kaliakin and C L Meehan ldquoColumnsupported embankments with geosynthetic encased col-umns Validity of the unit cell conceptrdquo Geotechnical andGeological Engineering 2015

[76] J Lai H Liu J Qiu and J Chen ldquoSettlement analysis ofsaturated tailings dam treated by CFG pile compositefoundationrdquo Advances in Materials Science and Engineeringvol 2016 Article ID 7383762 10 pages 2016

[77] W P Cao and M Zhao ldquoPerformance of floating piles forsupporting embankments in soft soilsrdquo Applied MechanicsandMaterials vol 105ndash107 pp 1433ndash1437 2011 httpsdoiorg104028wwwscientificnetAMM105-1071433

[78] X Gu X Tan W Huang and G Ren ldquoFailure mechanismsof embankment on inclined soft foundation reinforced byCFG Pilesrdquo Chinese Journal of Geotechnical Engineeringvol 39 2017

[79] H V Pham D Dias and A Dudchenko ldquo3D modeling ofgeosynthetic-reinforced pile-supported embankment undercyclic loadingrdquo Geosynthetics International vol 27 no 2pp 157ndash169 2020

[80] J Zhang J-J Zheng B-G Chen and J-H Yin ldquoCoupledmechanical and hydraulic modeling of a geosynthetic-reinforced and pile-supported embankmentrdquo Computersand Geotechnics vol 52 pp 28ndash37 2013

[81] Y Jiang J Han and G Zheng ldquoNumerical analysis of a pile-slab-supported railway embankmentrdquo Acta Geotechnicavol 9 no 3 pp 499ndash511 2014 httpsdoiorg101007s11440-013-0285-9

[82] C Xu G Ye Z Jiang and Q Zhou ldquoResearch on mech-anism of combined improvement of soft soils based on field

monitoringrdquo Chinese Journal of Geotechnical Engineeringvol 28 pp 918ndash921 2006

[83] H Yu Y Wang C Zou P Wang and C Yan ldquoStudy onsubgrade settlement characteristics after widening project ofhighway built on weak foundationrdquo Arabian Journal forScience and Engineering vol 42 no 9 pp 3723ndash3732 2017httpsdoiorg101007s13369-017-2469-3

[84] M A Nunez L Brianccedilon and D Dias ldquoAnalyses of a pile-supported embankment over soft clay full-scale experimentanalytical and numerical approachesrdquo Engineering Geologyvol 153 pp 53ndash67 2013 httpsdoiorg101016jenggeo201211006

[85] J J Zheng B G Chen Y E Lu S W Abusharar andJ H Yin ldquo+e performance of an embankment on softground reinforced with geosynthetics and pile wallsrdquo Geo-synthetics International vol 16 no 3 pp 173ndash182 2009httpsdoiorg101680gein2009163173

[86] M Raithel A Kirchner and H G Kempfert ldquoGermanrecommendations for reinforced embankments on pile-similar elementsrdquo in Geosynthetics in Civil and Environ-mental Engineering G Li Y Chen and X Tang EdsSpringer Berlin Heidelberg Germany 2008

[87] J Zhang J-j Zheng and Q Ma ldquoMechanical analysis offixed geosynthetic technique of GRPS embankmentrdquo Journalof Central South University vol 20 no 5 pp 1368ndash13752013 httpsdoiorg101007s11771-013-1624-6

[88] D F Fagundes M S S Almeida L +orel and M BlancldquoLoad transfer mechanism and deformation of reinforcedpiled embankmentsrdquo Geotextiles and Geomembranesvol 45 no 2 pp 1ndash10 2017 httpsdoiorg101016jgeotexmem201611002

[89] J Han A Bhandari and F Wang ldquoDEM analysis of stressesand deformations of geogrid-reinforced embankments overpilesrdquo International Journal of Geomechanics vol 12 no 4pp 340ndash350 2012 httpsdoiorg101061(ASCE)GM1943-56220000050

[90] R Roy and A Bhasi ldquoInvestigation of arching effect ingeosynthetic-reinforced piled embankmentsrdquo IranianJournal of Science and Technology Transactions of CivilEngineering vol 43 no S1 pp 249ndash262 2019 httpsdoiorg101007s40996-018-0162-8

[91] R Rui J Han S J M van Eekelen and Y Wan ldquoExperi-mental investigation of soil-arching development in unre-inforced and geosynthetic-reinforced pile-supportedembankmentsrdquo Journal of Geotechnical amp GeoenvironmentalEngineering vol 145 2019 httpsdoiorg101061(ASCE)GT1943-56060002000 Article ID 04018103

[92] Q Anh Tran P Villard and D Dias ldquoDiscrete and Con-tinuum Numerical Modeling of Soil Arching between PilesrdquoInternational Journal of Geomechanics vol 19 Article ID04018195 2019

[93] K Ghaffari Irdmoosa and H Shahir ldquoAnalytical solution foractive earth pressure of c-φ soil considering arching effectrdquoGeomechanics and Geoengineering vol 14 no 2 pp 71ndash842018 httpsdoiorg1010801748602520181533649

[94] Y M A Hashash and A J Whittle ldquoMechanisms of loadtransfer and arching for braced excavations in clayrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 128no 3 pp 187ndash197 2002 httpsdoiorg101061

[95] G-F He Z-G Li Y Yuan et al ldquoOptimization analysis ofthe factors affecting the soil arching effect between landslidestabilizing pilesrdquo Natural Resource Modeling vol 31 2018httpsdoiorg101111nrm12148 Article ID e12148


[96] C J Lee B R Wu H T Chen and K H Chiang ldquoTunnelstability and arching effects during tunneling in soft clayeysoilrdquo Tunnelling and Underground Space Technology vol 21no 2 pp 119ndash132 2006 httpsdoiorg101016jtust200506003

[97] A Roy and N R Patra ldquoEffect of arching on passive earthpressure for rigid retaining walls considering translationmoderdquo in Structures Congress 2009American Society of CivilEngineers Austin TX USA 2009

[98] K Terzaghi R B Peck and G Mesri Soil Mechanics inEngineering Practice Wiley New York NY USA 3rd edi-tion 1996

[99] Y-t Zhou Q-s Chen F-q Chen X-h Xue and S BasackldquoActive earth pressure on translating rigid retaining struc-tures considering soil arching effectrdquo European Journal ofEnvironmental and Civil Engineering vol 22 no 8pp 910ndash926 2018 httpsdoiorg1010801964818920161229225

[100] L Brianccedilon and B Simon ldquoPerformance of pile-supportedembankment over soft soil full-scale experimentrdquo Journal ofGeotechnical and Geoenvironmental Engineering vol 138no 4 pp 551ndash561 2012 httpsdoiorg101061(ASCE)GT1943-56060000561

[101] J Han and M A Gabr ldquoNumerical analysis of geosynthetic-reinforced and pile-supported earth platforms over soft soilrdquoJournal of Geotechnical and Geoenvironmental Engineeringvol 128 no 1 pp 44ndash53 2002

[102] K Fei and H Liu ldquoField test study and numerical analysis ofa geogridreinforced and pile-supported embankmentrdquo Rockand Soil Mechanics vol 30 pp 1005ndash1012 2009

[103] G Liu L Kong and X Li ldquoAnalysis of treatment scheme forsoft foundation on in expressway widening project and itsverificationrdquo Chinese Journal of Rock Mechanics and Engi-neering vol 27 pp 309ndash315 2008

[104] D B Zhang Y Zhang T Cheng and J Y Yuan ldquoSoftfoundation strengthening effect and structural optimizationof a new cement fly-ash and gravel pile-slab structurerdquo IJETranactions Basics vol 30 pp 955ndash963 2017

[105] M F Bransby and S M Springman ldquoCentrifuge modellingof pile groups adjacent to surcharge loadsrdquo Soils andFoundations vol 37 no 2 pp 39ndash49 1997 httpsdoiorg103208sandf372_39

[106] E A Ellis and S M Springman ldquoModelling of soil-structureinteraction for a piled bridge abutment in plane strain FEManalysesrdquo Computers and Geotechnics vol 28 no 2pp 79ndash98 2001 httpsdoiorg101016S0266-352X(00)00025-2

[107] D Li and D Davis ldquoTransition of railroad bridge ap-proachesrdquo Journal of Geotechnical and GeoenvironmentalEngineering vol 131 no 11 pp 1392ndash1398 2005

[108] B M Phares A S Faris L Greimann and D BierwagenldquoIntegral bridge abutment to approach slab connectionrdquoJournal of Bridge Engineering vol 18 no 2 pp 179ndash1812013 httpsdoiorg101061(ASCE)BE1943-55920000333

[109] D P Stewart R J Jewell and M F Randolph ldquoDesign ofpiled bridge abutments on soft clay for loading from lateralsoil movementsrdquo Geotechnique vol 44 no 2 pp 277ndash2961994 httpsdoiorg101680geot1994442277

[110] D Xiao G L Jiang D Liao Y F Hu and X F Liu ldquoIn-fluence of cement-fly ash-gravel pile-supported approachembankment on abutment piles in soft groundrdquo Journal ofRock Mechanics and Geotechnical Engineering vol 10 no 5pp 977ndash985 2018 httpsdoiorg101016jjrmge201806001

[111] D Xiao G Jiang Z Lin et al ldquoAnalysis on workingproperties of abutment piles considering foundation rein-forcement of approach embankmentrdquo Journal of CentralSouth University of Technology vol 48 pp 820ndash829 2017

[112] W Li and X Bian ldquoDynamic performance of pile-supportedbridge-embankment transition zones under high-speed trainmoving loadsrdquo Procedia Engineering vol 143 pp 1059ndash1067 2016 httpsdoiorg101016jproeng201606101

[113] X Han Y Li J Ji J Ying W Li and B Dai ldquoNumericalsimulation on the seismic absorption effect of the cushion inrigid-pile composite foundationrdquo Earthquake Engineeringand Engineering Vibration vol 15 no 2 pp 369ndash378 2016httpsdoiorg101007s11803-016-0329-x

[114] X Zhu K Fei and S Wang ldquoHorizontal loading tests ondisconnected piled rafts and a simplified method to evaluatethe horizontal bearing capacityrdquo Advances in Civil Engi-neering vol 2018 Article ID 3956509 12 pages 2018

[115] J Ding X Quan E Du and T Zhao ldquoDynamic charac-teristics on composite foundation with CFG pilerdquo Journal ofCivil Architectural amp Environmental Engineering vol 1pp 104ndash109 2014

[116] J Ding W Wang T Zhao J Feng and P Zhang ldquo+edynamic characteristic experimental method on the com-posite foundation with rigid-flexible compound pilesrdquo OpenJournal of Civil Engineering vol 3 no 2 pp 94ndash98 2013

[117] Y Feng Y Wang and C Zhang ldquo+e analysis of compositefoundation with CFG and gravel piles to resist soil lique-factionrdquo in Geotechnical Enginnering for Disaster Mitigationand Rehabilitation H Liu A Deng and J Chu EdsSpringer Berlin Germany 2008

[118] C Yang K Ni and S Wang ldquoAnalysis of the stress char-acteristics of CFG pile composite foundation under irreg-ularity conditionrdquo Stavebnı Obzor-Civil Engineering Journalvol 26 no 2 pp 154ndash166 2017 httpsdoiorg1014311CEJ2017020014

[119] L Li J Huang and B Han ldquoCentrifugal investigation ofexcavation adjacent to existing composite foundationrdquoJournal of Performance of Constructed Facilities vol 32 2018httpsdoiorg101061(ASCE)CF1943-55090001188 Ar-ticle ID 04018044

[120] L Ma ldquoResearch on design of CFG pile composite foun-dation for high-rise buildingsrdquo Value Engineering vol 39pp 145-146 2020

[121] G-h Wang and Y-y Yang ldquoEffect of cantilever soldier pilefoundation excavation closing to an existing compositefoundationrdquo Journal of Central South University vol 20no 5 pp 1384ndash1396 2013 httpsdoiorg101007s11771-013-1626-4

[122] Y Yuan A Liu Y Jiao and C Liu ldquoField detection andsimulation analysis of CFG pile composite foundationrdquoJournal of Civil Engineering vol 7 pp 906ndash918 2018

[123] Z Q Xie C Jun H B Xiao and Z Y Li ldquoApplication ofCFG piles in treatment of a large oil tank foundationrdquoAdvanced Materials Research vol 446-449 pp 2518ndash25222012 httpsdoiorg104028wwwscientificnetAMR446-4492518

[124] C Bohn Serviceability and Safety in the Design of RigidInclusions and Combined Pile-Raft Foundations PhDDissertation Department of Civil Engineering UniversiteParis-Est Champs-sur-Marne France 2015

[125] H Rasouli and B Fatahi ldquoA novel cushioned piled raftfoundation to protect buildings subjected to normal faultrupturerdquo Computers and Geotechnics vol 106 pp 228ndash2482019 httpsdoiorg101016jcompgeo201811002


[126] M El Sawwaf ldquoExperimental study of eccentrically loadedraft with connected and unconnected short pilesrdquo Journal ofGeotechnical and Geoenvironmental Engineering vol 136no 10 pp 1394ndash1402 2010 httpsdoiorg101061(ASCE)GT1943-56060000341

[127] F Tradigo F Pisano C di Prisco and A Mussi ldquoNon-linearsoil-structure interaction in disconnected piled raft foun-dationsrdquo Computers and Geotechnics vol 63 pp 121ndash1342015 httpsdoiorg101016jcompgeo201408014

[128] I H Wong M F Chang and X D Cao ldquoRaft foundationswith disconnected settlement-reducing pilesrdquo in DesignApplications of Raft Foundations+omas Telford PublishingLondon UK 2000

[129] M H Baziar F Rafiee C J Lee and A Saeedi AzizkandildquoEffect of superstructure on the dynamic response of non-connected piled raft foundation using centrifuge modelingrdquoInternational Journal of Geomechanics vol 18 2018 httpsdoiorg101061(ASCE)GM1943-56220001263 Article ID04018126

[130] X D Cao I HWong andM-F Chang ldquoBehavior of modelrafts resting on pile-reinforced sandrdquo Journal of Geotechnicaland Geoenvironmental Engineering vol 130 no 2pp 129ndash138 2004 httpsdoiorg101061

[131] Y Min ldquoStudy on reducing_settlement pile foundationbased on controlling settlement principlerdquo Chinese Journalof Geotechnical Engineering vol 22 pp 481ndash486 2000

[132] H G Poulos ldquoPiled raft foundations design and applica-tionsrdquo Geotechnique vol 51 no 2 pp 95ndash113 2001 httpsdoiorg101680geot200151295

[133] M Ghanbar Dezfouli M Dehghani A Asakereh andB Kalantari ldquoBehavior of geogrid reinforced and unrein-forced non-connected pile raft foundationrdquo InternationalJournal of Civil Engineering vol 17 no 6 pp 709ndash722 2019httpsdoiorg101007s40999-018-0362-4

[134] H Rasouli A Saeedi Azizkandi M H Baziar et alldquoCentrifuge modeling of non-connected piled raft systemrdquoInternational Journal of Civil Engineering vol 13 2015

[135] A Saeedi Azizkandi H Rasouli and M H Baziar ldquoLoadsharing and carrying mechanism of piles in non-connectedpile rafts using a numerical approachrdquo International Journalof Civil Engineering vol 17 no 6 pp 793ndash808 2019 httpsdoiorg101007s40999-018-0356-2

[136] M Yang and S Liu ldquoField tests and finite element modelingof a prestressed concrete pipe pile-composite foundationrdquoKSCE Journal of Civil Engineering vol 19 no 7 pp 2067ndash2074 2015 httpsdoiorg101007s12205-015-0549-z

[137] S Nakai H Kato R Ishida et al ldquoLoad bearing mechanismof piled raft foundation during earthquakerdquo in Proceedings ofthe Mird UJNR Workshop on Soil-Structure InteractionMenlo Park CA USA 2004

[138] X Zhu W Kong W Gong et al ldquoTest on the horizontalcharacteristics of disconnected piles raft foundationrdquo ChinaJournal of Highway and Transport vol 32 pp 97ndash115 2019

[139] A S Azizkandi M H Baziar and A F Yeznabad ldquo3Ddynamic finite element analyses and 1 g shaking table testson seismic performance of connected and nonconnectedpiled raft foundationsrdquo KSCE Journal of Civil Engineeringvol 22 no 5 pp 1750ndash1762 2018 httpsdoiorg101007s12205-017-0379-2

[140] R Xu and B Fatahi ldquoGeosynthetic-reinforced cushionedpiles with controlled rocking for seismic safeguardingrdquoGeosynthetics International vol 25 no 6 pp 561ndash581 2018httpsdoiorg101680jgein1800018

[141] D Basu A Misra and A J Puppala ldquoSustainability andgeotechnical engineering perspectives and reviewrdquo Cana-dian Geotechnical Journal vol 52 no 1 pp 96ndash113 2015httpsdoiorg101139cgj-2013-0120

[142] M Samanta ldquoInvestigation on geomechanical behaviour andmicrostructure of cement-stabilized fly ashrdquo InternationalJournal of Geotechnical Engineering vol 12 no 5pp 449ndash461 2018 httpsdoiorg1010801938636220171295623

[143] S Liang J Chen M Guo D Feng L Liu and T QildquoUtilization of pretreated municipal solid waste incinerationfly ash for cement-stabilized soilrdquo Waste Managementvol 105 pp 425ndash432 2020 httpsdoiorg101016jwasman202002017

[144] K-Y Show J-H Tay and A T C Goh ldquoReuse of incin-erator fly ash in soft soil stabilizationrdquo Journal of Materials inCivil Engineering vol 15 no 4 pp 335ndash343 2003

[145] C Spaulding F Masse and J LaBrozzi ldquoGround im-provement technologies for a sustainable Worldrdquo in Geo-Congress 2008American Society of Civil Engineers NewOrleans LA USA 2008

[146] B Zhang S Cui Z Liu and F Feng ldquoField tests of cementfly-ash steel-slag pile composite foundationrdquo Journal ofTesting and Evaluation vol 45 no 3 httpsdoiorg101520JTE20140422 Article ID 20140422 2017

[147] D P Jiang and B L Wang ldquoAn analysis on failure pattern ofCFG pile-net composite foundation of high-speed railwayrdquoAdvanced Materials Research vol 594ndash597 pp 1357ndash13622012 httpsdoiorg104028wwwscientificnetAMR594-5971357

[148] Q Xu Y Song and X Han ldquoApplication of CFG piles to softsoil treatment of municipal engineeringrdquo in MechanicalEngineering and Control SystemsWorld Scientific WuhanChina 2016

[149] L Deng ldquoCFG pile based soft foundation treatmentrdquo Ap-plied Mechanics and Materials vol 484-485 pp 790ndash7952014 httpsdoiorg104028wwwscientificnetAMM484-485790

[150] W N Abd El Samee ldquoEffect of shape and depth of shallowfoundations on failure mechanism and Wedge angle ofsandy soilrdquo in Advanced Research on Shallow FoundationsH Shehata and B Das Eds Springer International Pub-lishing Cham Switzerland 2019

[151] Y Chi W Shen and E Song ldquoDiscussion on pile soil re-lationship between failure model of cushion and stress ratiordquoIndustrial Construction vol 31 pp 9ndash11 2001

[152] IREX Recommendations for the Design Construction andControl of Rigid Inclusion Ground Improvements Presses desPonts Paris France 2012

[153] F Wang F Zhu S Wang and T Dong ldquoCushion design ofcomposite foundationrdquo Journal of Northeast Normal Uni-versity (Natural Science Edition) vol 25 pp 287ndash290 2004

[154] R Rui Y Sun Y Zhu et al ldquoMesoscopic working mech-anism of cushion of composite foundation under rigid slabrdquoRock and Soil Mechanics vol 40 pp 445ndash454 2019

[155] X Zhu and W Gong ldquoStudy on soil arching in the cushionof composite foundationrdquo in Soil Behavior and Geo-mechanicsAmerican Society of Civil Engineers ShanghaiChina 2014

[156] M Al-Naddaf J Han C Xu et al ldquoExperimental investi-gation of soil arching mobilization and degradation underlocalized surface loadingrdquo Journal of Geotechnical amp Geo-environmental Engineering vol 145 2019 httpsdoiorg101061(ASCE)GT1943-56060002190 Article ID 04019114


[157] T A Pham ldquoAnalysis of geosynthetic-reinforced pile-sup-ported embankment with soil-structure interaction modelsrdquoComputers and Geotechnics vol 121 2020 httpsdoiorg101016jcompgeo2020103438 Article ID 103438

[158] S J M van Eekelen and J Han ldquoGeosynthetic-reinforcedpile-supported embankments state of the artrdquo GeosyntheticsInternational vol 27 no 2 pp 112ndash141 2020 httpsdoiorg101680jgein2000005

[159] S J M van Eekelen A Bezuijen and A F van Tol ldquoAnanalytical model for arching in piled embankmentsrdquo Geo-textiles and Geomembranes vol 39 pp 78ndash102 2013 httpsdoiorg101016jgeotexmem201307005

[160] P Ariyarathne and D S Liyanapathirana ldquoReview ofexisting design methods for geosynthetic-reinforced pile-supported embankmentsrdquo Soils and Foundations vol 55no 1 pp 17ndash34 2015 httpsdoiorg101016jsandf201412002

[161] P Shen C Xu and J Han ldquoCentrifuge tests to investigateglobal performance of geosynthetic-reinforced pile-sup-ported embankments with side slopesrdquo Geotextiles andGeomembranes vol 48 no 1 pp 120ndash127 2020 httpsdoiorg101016jgeotexmem2019103527

[162] S J M van Eekelen A Bezuijen H J Lodder andA F van Tol ldquoModel experiments on piled embankmentspart Irdquo Geotextiles and Geomembranes vol 32 pp 69ndash812012 httpsdoiorg101016jgeotexmem201111002

[163] A Bhasi and K Rajagopal ldquoNumerical study of basalreinforced embankments supported on floatingend bearingpiles considering pile-soil interactionrdquo Geotextiles andGeomembranes vol 43 no 6 pp 524ndash536 2015 httpsdoiorg101016jgeotexmem201505003

[164] P Shen C Xu and J Han ldquoGeosynthetic-reinforced pile-supported embankment settlement in different pile condi-tionsrdquo Geosynthetics International vol 27 no 3pp 315ndash331 2020

[165] I V L Chango M Yan X Ling T Liang andO C Assogba ldquoDynamic response analysis of geogridreinforced embankment supported by CFG pile structureduring a high-speed train operationrdquo Latin AmericanJournal of Solids and Structures vol 16 no 7 httpsdoiorg1015901679-78255710 Article ID e214 2019

[166] C Zhang G Jiang X Liu and O Buzzi ldquoArching ingeogrid-reinforced pile-supported embankments over siltyclay of medium compressibility field data and analyticalsolutionrdquo Computers and Geotechnics vol 77 pp 11ndash252016 httpsdoiorg101016jcompgeo201603007

[167] G-B Ye M Wang Z Zhang J Han and C Xu ldquoGeo-synthetic-reinforced pile-supported embankments with capsin a triangular pattern over soft clayrdquo Geotextiles andGeomembranes vol 48 no 1 pp 52ndash61 2020 httpsdoiorg101016jgeotexmem2019103504

[168] M Wijerathna and D S Liyanapathirana ldquoLoad transfermechanism in geosynthetic reinforced column-supportedembankmentsrdquo Geosynthetics International vol 27 no 3pp 236ndash248 2020

[169] C Wang S Zhou B Wang and P Guo ldquoTime effect of pile-soil-geogrid-cushion interaction of rigid pile compositefoundations under high-speed railway embankmentsrdquoGeomechanics and Engineering vol 16 pp 589ndash597 2018

[170] A Ata E Badrawi and M Nabil ldquoNumerical analysis ofunconnected piled raft with cushionrdquo Ain Shams Engi-neering Journal vol 6 no 2 pp 421ndash428 2015 httpsdoiorg101016jasej201411002

[171] H Dan L Li L Zhao and F Wan ldquoCalculation and in-fluence factors analysis on pile-soil stress ratio of CFG pilecomposite foundationrdquo China Railway Science vol 29pp 7ndash12 2008

[172] J Fu and E Song ldquoAnalysis of rigid pile composite foun-dationrsquos working performancerdquo Rock and Soil Mechanicsvol 21 pp 335ndash339 2000

[173] C Guo S W Xiao and Z L Chen ldquoStudy of low strengthpile composite foundation deformation amp stability calcula-tion methodrdquo Applied Mechanics and Materialsvol 170ndash173 pp 545ndash556 2012 httpsdoiorg104028wwwscientificnetAMM170-173545

[174] B Broms ldquoNegative skin frictionrdquo in Proceedings of 6thAsian Regional Asian Conference on Soil Mechanics andFoundation Engineering pp 41ndash75 Singapore 1979

[175] C J Lee M D Bolton and A Al-Tabbaa ldquoNumericalmodelling of group effects on the distribution of dragloads inpile foundationsrdquo Geotechnique vol 52 no 5 pp 325ndash3352002

[176] D Loukidis and R Salgado ldquoAnalysis of the shaft resistanceof non-displacement piles in sandrdquo Geotechnique vol 58no 4 pp 283ndash296 2008 httpsdoiorg101680geot2008584283

[177] J Li J Cong N Li and J Cao ldquoStudy on the design methodof CFG pile composite foundation for storage tanks based onthe settlement controllingrdquo Journal of Hohai University(Natural Sciences) vol 46 pp 321ndash328 2018

[178] S Yan R Lang L Sun et al ldquoCalculation of pile-soil stressratio in composite foundation with rigid pile-net based onplate theoryrdquo Chinese Journal of Rock Mechanics and En-gineering vol 36 pp 2051ndash2060 2017

[179] T Ma Y Zhu X Yang and Y Ling ldquoBearing characteristicsof composite pile group foundations with long and shortpiles under lateral loading in loess areasrdquo MathematicalProblems in Engineering vol 2018 Article ID 814535617 pages 2018

[180] R B Peck ldquoDeep excavations and tunneling in soft groundrdquoin Proceedings of the 7th International Conference on SoilMechanics and Foundation Engineering pp 225ndash290Mexico MX USA 1969

[181] H Chen J Li C Yang and C Feng ldquoA theoretical study onground surface settlement induced by a braced deep exca-vationrdquo European Journal of Environmental and Civil En-gineering pp 1ndash20 2020

[182] G W Clough and T D OrsquoRourke ldquoConstruction inducedmovements of insitu wallsrdquo in Design and Performance ofEarth Retaining StructuresASCE Geotechnical Special Pub-lication New York NY USA 1990

[183] X Zhang J Yang Y Zhang and Y Gao ldquoCause investi-gation of damages in existing building adjacent to founda-tion pit in constructionrdquo Engineering Failure Analysisvol 83 pp 117ndash124 2018 httpsdoiorg101016jengfailanal201709016

[184] W G Zhang A T C Goh K H Goh O Y S ChewD Zhou and R Zhang ldquoPerformance of braced excavationin residual soil with groundwater drawdownrdquo UndergroundSpace vol 3 no 2 pp 150ndash165 2018 httpsdoiorg101016jundsp201803002

[185] H G Poulos ldquoGround movements - a hidden source ofloading on deep foundationsrdquoDFI Journal-Me Journal of theDeep Foundations Institute vol 1 no 1 pp 37ndash53 2007httpsdoiorg101179dfi2007004

[186] A Yao J Lu Y Guo et al ldquoReinforcement effects of iso-lation piles on the adjacent existing tunnel in building


constructionrdquo Advances in Materials Science and Engi-neering vol 2019 Article ID 9741306 21 pages 2019

[187] O Demeijer J-J Chen M-G Li et al ldquoInfluence of pas-sively loaded piles on excavation-induced diaphragm walldisplacements and ground settlementsrdquo InternationalJournal of Geomechanics vol 18 2018 httpsdoiorg101061(ASCE)GM1943-56220001126 Article ID 04018052

[188] G Pittaro ldquoTensile strength behaviour of ground im-provement and its importance on deep excavations usingdeep soil mixingrdquo in Proceedings of the XVII EuropeanConference on Soil Mechanics and Geotechnical Engineeringpp 415ndash422 Reykjavik Iceland September 2019

[189] Y S Fang and I Ishibashi ldquoStatic earth pressures withvarious wall movementsrdquo Journal of Geotechnical Engi-neering vol 112 no 3 pp 317ndash333 1986

[190] R J Finno S Kim J Lewis and N Van Winkle ldquoObservedperformance of a sheetpile-supported excavation in chicagoclaysrdquo Journal of Geotechnical amp Geoenvironmental Engi-neering vol 145 2019 httpsdoiorg101061(ASCE)GT1943-56060002010 Article ID 05018005

[191] M Georgiadis and C Anagnostopoulos ldquoLateral pressure onsheet pile walls due to strip loadrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 124 no 1 pp 95ndash981998

[192] P-G Hsieh and C-Y Ou ldquoShape of ground surface set-tlement profiles caused by excavationrdquo Canadian Geotech-nical Journal vol 35 no 6 pp 1004ndash1017 1998 httpsdoiorg101139t98-056

[193] M H Khosravi T Pipatpongsa and J Takemura ldquo+eo-retical analysis of earth pressure against rigid retaining wallsunder translation moderdquo Soils and Foundations vol 56no 4 pp 664ndash675 2016 httpsdoiorg101016jsandf201607007

[194] Y Tang J Pei Li and Y Ma ldquoLateral earth pressure con-sidering the displacement of a rigid retaining wallrdquo Inter-national Journal of Geomechanics vol 18 2018 httpsdoiorg101061(ASCE)GM1943-56220001284 Article ID06018031

[195] Q Fu and L Li ldquoVertical load transfer behavior of compositefoundation and its responses to adjacent excavation cen-trifuge model testrdquo Geotechnical Testing Journal vol 44no 1 httpsdoiorg101520GTJ20180237 Article ID20180237 2021

[196] L Li and Q Fu ldquoLateral mechanical behavior of compositeground due to adjacent excavation centrifuge model testrdquoChina Civil Engineering Journal vol 50 pp 85ndash94 2017

[197] G F Ren and J S Qiao ldquoResearch on the mechanical be-havior effect of around composite foundation under soillateral displacementrdquo Applied Mechanics and Materialsvol 353ndash356 pp 696ndash701 2013 httpsdoiorg104028wwwscientificnetAMM353-356696

[198] D S Liyanapathirana and R Nishanthan ldquoInfluence of deepexcavation induced ground movements on adjacent pilesrdquoTunnelling and Underground Space Technology vol 52pp 168ndash181 2016 httpsdoiorg101016jtust201511019

[199] R Zhang W Zhang and A T C Goh ldquoNumerical in-vestigation of pile responses caused by adjacent bracedexcavation in soft claysrdquo International Journal of Geotech-nical Engineering pp 1ndash15 2018 httpsdoiorg1010801938636220181515810

[200] R Fuentes A Pillai and P Ferreira ldquoLessons learnt from adeep excavation for future application of the observationalmethodrdquo Journal of Rock Mechanics and Geotechnical

Engineering vol 10 no 3 pp 468ndash485 2018 httpsdoiorg101016jjrmge201712004

[201] R B Peck ldquoAdvantages and limitations of the observationalmethod in applied soil mechanicsrdquo Geotechnique vol 19no 2 pp 171ndash187 1969 httpsdoiorg101680geot1969192171

[202] A J Powderham ldquo+e observational method-learning fromprojectsrdquo Proceedings of the Institution of Civil Engineers-Geotechnical Engineering vol 155 no 1 pp 59ndash69 2002httpsdoiorg101680geng2002155159

[203] J Spross and F Johansson ldquoWhen is the observationalmethod in geotechnical engineering favourablerdquo StructuralSafety vol 66 pp 17ndash26 2017 httpsdoiorg101016jstrusafe201701006

[204] M Calvello ldquoFrom the observational method to ldquoobserva-tional modellingrdquo of geotechnical engineering boundaryvalue problemsrdquo in Geotechnical Safety and ReliabilityA-merican Society of Civil Engineers Denver Colorado 2017

[205] F Wang Engineering Characteristics of Solid Pile CompositeFoundation PhD Dissertation Northeastern UniversityBoston MA USA 2003

[206] X-j Zhu ldquoAnalysis of the load sharing behaviour andcushion failure mode for a disconnected piled raftrdquo Ad-vances in Materials Science and Engineeringvol 201713 pages 2017 httpsdoiorg10115520173856864 Article ID 3856864

[207] J Zheng J Chen H Luo and Y Lu ldquoAnalyzing failuremodes and appropriate thickness of the cushion on rigid pilecomposite groundrdquo Journal of Huazhong University of Sci-ence and Technology (Nature Science) vol 36 pp 120ndash1242008

[208] Y Dong J Zheng and J Zhang ldquoAnalysis of flow and failuremechanism of cushion in rigid pile composite foundationrdquoAdvanced Materials Research vol 168ndash170 pp 1491ndash14952011

[209] S Varaksin B Hamidi N Huybrechts and N DeniesGround Improvement vs Pile Foundations WTCB-CSTCLeuven Belgium 2016

[210] M Kitazume K Orano and S Miyajima ldquoCentrifuge modeltests on failure envelope of column type deep mixing methodimproved groundrdquo Soils and Foundations vol 40 no 4pp 43ndash55 2000 httpsdoiorg103208sandf404_43

[211] J Yao Research of Flow plastic soft soil composite foundationfailure mechanism and processing method PhD Disserta-tion China Academy of Railway Science Beijing China2015

[212] N N S Yapage D S Liyanapathirana and C J Leo ldquoFailuremodes for geosynthetic reinforced column supported(GRCS) embankmentsrdquo in Proceedings of the 18th Inter-national Conference on Soil Mechanics and GeotechnicalEngineering pp 849ndash852 Paris France 2013

[213] G Zheng S Li and Y Daio ldquoCentrifugal model tests onfailure mechanisms of embankments on soft ground rein-forced by rigid pilesrdquo Chinese Journal of Geotechnical En-gineering vol 34 pp 1977ndash1989 2012

[214] D Miao and J Liu ldquoStudy of failure mode of CFG pile inconmposite foundation under embankment by centrifugalmodel testrdquo Guangdong Highway Communicationsvol 10ndash13 2016

[215] X Wu X Dai K Zhang et al ldquoStudy on centrifugal modeltest of rigid pile foundationrdquo Journal of Civil Engineering andManagement vol 35 pp 13ndash19 2018


[216] BS 8006-1 Code of Practice for Strengthenedreinforced Soilsand Other Fills British Standards Institution ISBN LondonUK 2010

[217] J-F Chen L-Y Li J-F Xue and S-Z Feng ldquoFailuremechanism of geosynthetic-encased stone columns in softsoils under embankmentrdquo Geotextiles and Geomembranesvol 43 no 5 pp 424ndash431 2015 httpsdoiorg101016jgeotexmem201504016

[218] M Kitazume ldquoA parametric study on evaluation of stabilityof column type DM improved groundrdquo in Advances inEnvironmental Geotechnics Y Chen L Zhan and X TangEds Springer Berlin Heidelberg Germany 2010

[219] B B Broms ldquoLime and limecement columnsrdquo in GroundImprovement M P Moseley and K Kirsch Eds Spon PressLondon UK 2004

[220] M Kitazume Stability of Group Column Type DMImprovedGround under Embankment Loading Port and AirportResearch Institute Yokosuka Kanagawa Japan 2008

[221] W Hang ldquoAnalysis of causes of CFG pile necking in saturatedsoft soil layer and its control measuresrdquo World Constructionvol 5 2016 httpsdoiorg1018686wcv5i274

[222] F Teng ldquoQuality control of CFG pile composite foundationin constructionrdquo Value Engineering vol 38 pp 14-15 2019

[223] G Ren and Z Shi ldquoAnalysis on disqualified bearing capacityof individual pile in CFG pile composite foundationrdquo Ar-chitectural Technology vol 47 pp 1107ndash1109 2016

[224] G x Zhu and Y Han ldquoStudy on quality detection andreinforcement effect of CFG pilerdquo IOP Conference SeriesMaterials Science and Engineering vol 394 2018 httpsdoiorg1010881757-899X3943032079 Article ID 032079

[225] L Zhang W Qing S Sun and H Li ldquoResearching theapplication of CFG pile treatment in soft foundation ofexpresswayrdquo in Proceedings of the First International Con-ference on Information Sciences Machinery Materials andEnergy Atlantis Press Chongqing China 2015

[226] S You X Cheng H Guo and Z Yao ldquoExperimental studyon structural response of CFG energy pilesrdquo AppliedMermal Engineering vol 96 pp 640ndash651 2016 httpsdoiorg101016japplthermaleng201511127

[227] Q Li and L An ldquoAnalysis of temperature field of em-bankment-CFG piles composite soft soil foundation systemin cold regionsrdquo IOP Conference Series Earth and Envi-ronmental Science vol 189 2018 httpsdoiorg1010881755-13151892022037 Article ID 022037

[228] S AoyamaWMao S Goto and I Towhata ldquoApplication ofadvanced procedures to model tests on the subsoil behaviorunder vertical loading of group pile in sandrdquo Indian Geo-technical Journal vol 46 no 1 pp 64ndash76 2016 httpsdoiorg101007s40098-015-0152-8

[229] M Li and J Zhao ldquoProgress of research advance on themodel tests on the interaction between new constructionsand adjacent existing buildingsrdquo in Proceedings of theGeoShanghai 2018 International Conference Tunnelling andUnderground Construction D Zhang and X Huang EdsSpringer Singapore Singapore 2018

[230] M T Suleiman L Ni J D Helm and A Raich ldquoSoil-pileinteraction for a small diameter pile embedded in granular soilsubjected to passive loadingrdquo Journal of Geotechnical amp Geo-environmental Engineering vol 140 2014 httpsdoiorg101061(ASCE)GT1943-56060001081 Article ID 04014002

[231] R Rui Y X Zhai J Han S J M van Eekelen and C ChenldquoDeformations in trapdoor tests and piled embankmentsrdquoGeosynthetics International vol 27 no 2 pp 219ndash235 2020httpsdoiorg101680jgein1900014


in the CFG pile composite foundation receive structural loadin an integrated way that involves the contribution of top soilbetween piles +e bearing capacity of the soil between pilesis sufficiently utilised by providing an appropriate thicknessof the mattress layer between the pilesrsquo head and the base ofthe supported structure Because of the stress concentrationon top of piles piles will puncture upward into the cushionlayer (see Figure 1) thus the load is partly transferredthrough negative side friction developing on the upper pilepart After the neutral depth the negative skin friction re-verts into positive +e depth of the neutral plane is mostlylocated above the mid and for the rigid end-bearing pilecomposite foundation it may range from 015 to 035 timesthe pile length [16 22 23] In Figure 1 SS is the totalcompression deformation of the soil between piles δp is thetotal compression deformation of the rigid pile S1 and S2 arethe settlement difference between the top and the bottom ofthe soil layer in the reinforcement area after loading and S3and S4 are the settlement of the pile top and the pile bottomrespectively δ1 and δ2 are the rigid pile head puncture intothe cushion layer and its tip settlement in the underlying soillayer respectively l and l0 are the pile length and the depthof the neutral plane respectively and hc is the thickness ofthe interposed layer

Many authors studied the effect of cushion thickness andits engineering properties on the load redistributionmechanism [24ndash27] Studies indicated that beyond a certainthickness the cushion effectiveness appeared to be quitenegligible Similarly the increase in the cushion thicknessbeyond the optimum depth level had limited influence onthe depth of the neutral surface and pile-soil stress ratio+us for a reasonable and efficient load distribution of pile-soil an appropriate thickness of the cushion layer shall beprovided Experimental and numerical analyses have indi-cated that the pile-soil stress ratio increased as the loadingincreased to a certain level to attain a stable state afterward[23 28 29] One can easily observe from Figure 2 that thepile-soil stress ratio depends on multiple parameters forexample it decreases as the thickness of the cushion layerincreases and gets approximately a constant value at somepoint [23 30ndash32]

+e pile-soil stress ratio is an important reflection pa-rameter for the working condition of the CFG pile compositefoundation Tradigo et al [33] discussed the mechanism ofcushion layer compression during vertical load transmis-sion +ey showed that as the two stiff bodies (pile and raft)approached the cushion from top and bottom plastic strainsdeveloped and spread from the head of the piles Based ondeformation and shear strain contours in the cushion layerRui et al [34] discussed developing a soil-arching phe-nomenon with a multitrapdoor test apparatus and verifiedthe similarity of the slip surface and deformation patternwith that of the diffusion cone model+ey disclosed that thecushionrsquos load redistribution capability depended on theinterposed layer thickness and its properties as well as pilespacing Boussetta et al [35] investigated the cushionthickness effect on the pile-soil stress ratio for a rigid andflexible foundation system +eir study indicated that up toa certain thickness of the mattress layer the efficiency of

rigid inclusion in receiving the applied load increased for therigid foundation compared to embankments (flexiblefoundation) Similar inference has been forwarded withnumerical analyses [36] As piles are practically used in agroup the group effect affected the pile-soil stress ratio[37 38] +e pile spacing as it was somehow related to thearea replacement ratio to be discussed later influenced theload shared by the piles

In order to save investment cost some practitionerscombined various foundation treatment methods to form amixed pile composite foundation consisting of different piletypes andor different lengths of piles +e engineeringpractice of such a new composite foundation exploits thecontribution of the shallow soil strengthened by moreflexible or short piles together with the mobilized bearingcapacity of long piles in the deeper strata [1739ndash43] Tomention some Liu et al [40] and Zhang et al [44] discussedabout piles of different flexibilities Ge et al [45] and Lu et al[46] reported about employing different lengths Hou [47]investigated the vertical force transmission mechanism of arigid long-short pile composite foundation Regardingdissimilar material types Zheng et al [48] conveyed aboutCFG-lime usage and Zhang et al [4] gave attention to CFGpiles used in all parts but rigid concrete piles under the slabedge Zhang and Zhang [49] experimentally studied CFGpiles combined with vibroreplacement stone columns Allthese multipile composite foundations emerged to fulfill theneed for modifying the rigidity and stability of the poorsubsoil as well as drainage requirements to accelerate excesspore water pressure dissipation On top of that it is note-worthy that none is omnipotent by itself but has a certainapplication scope as far as any soft ground treatment methodis concerned

2 Bearing Capacity andSettlement Characteristics

Like any other foundation system CFG pile compositefoundation has to be checked for both its capacity to bearsuperstructural load and its settlement characteristics as theload being transmitted through time So far as the literatureshows the bearing capacity can reasonably be estimated byusing the following equation [50ndash53]

fspk m1Ra1

Ap1+ β1m2

Ra2

Ap2+ β2 1 minus m1 minus m2( 1113857 fsk (1)

where m1 m2 are the replacement rate of the long pile andshort pile respectively β1 β2 are the strength reductioncoefficient of the short pile and soil between piles respec-tively Ra1 Ra2 are the characteristic values of the verticalbearing capacity of the long pile and short pile respectively(see equation (2)) which can be determined according to thestatic load test or the bearing capacity of a single pile de-termined by the strength of the pile body Ap1 Ap2 are thecross-sectional area of the long pile and short pile re-spectively and fspk and fsk are the characteristic values ofthe bearing capacity of the composite foundation and soilbetween piles respectively


020100 200 300 400 500 600 700 800 900

022

024

026

028

029



Dep

th ra

tio o

f the

neu

tral

pla

ne

0

10

20

30

40

50

Pile

-soi

l stre

ss ra

tio


S1 δ2

S 2

δ2

Neutralplane



l 0

lh c

S 3S4

External load


S1 = S3 + δ1

S4 = S2 ndash δ2


Cushionlayer

Foundation ra

CFG

pile

Toe resistance




Ra12 upi

1113944i

qsili + Apqp (2)





S ψsp 1113944

n1

i1

P0

ξEsi


+ 1113944

n2

in1+1

P0

Esi


(3)
























dz

Z

Pile

Ps

Pp

Ps

l0

l

σsz σsz


τfndash Um

Umτf+

τf+

τfndash

τ

τ

τf

ks

um

Z1

Z2

τ u

Transitionzone

Z ZZ

(I) (II) δb

δt

(a) (b) (c)

(e)

(d)

u

Elasticphase

Plastic phase


Surcharge load

Soil arching

Pile cap

Pile


fixed fulcrum


Geosynthetic






4 Discussion


















the next position



















20

18

16

14

12

10

08

06

04

02

Cap

Cap

Lowerboundary

Upperboundary

135

(s-a

)

05

(s-a

)

Crown 14 (s-a)N

orm

aliz

ed em

bank

men

t hei

ght

(s-a) Y (m)X (m)

ndash25ndash20

ndash15ndash10

ndash050

0510

1520

25 0005

1015

2025

3035






11138681113868111386811138681113868



⎧⎨

⎩ (5)







01

02

03

04

05

06

07



Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D








σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References






















































































































































































































































020100 200 300 400 500 600 700 800 900

022

024

026

028

029



Dep

th ra

tio o

f the

neu

tral

pla

ne

0

10

20

30

40

50

Pile

-soi

l stre

ss ra

tio


S1 δ2

S 2

δ2

Neutralplane



l 0

lh c

S 3S4

External load


S1 = S3 + δ1

S4 = S2 ndash δ2


Cushionlayer

Foundation ra

CFG

pile

Toe resistance




Ra12 upi

1113944i

qsili + Apqp (2)





S ψsp 1113944

n1

i1

P0

ξEsi


+ 1113944

n2

in1+1

P0

Esi


(3)
























dz

Z

Pile

Ps

Pp

Ps

l0

l

σsz σsz


τfndash Um

Umτf+

τf+

τfndash

τ

τ

τf

ks

um

Z1

Z2

τ u

Transitionzone

Z ZZ

(I) (II) δb

δt

(a) (b) (c)

(e)

(d)

u

Elasticphase

Plastic phase


Surcharge load

Soil arching

Pile cap

Pile


fixed fulcrum


Geosynthetic






4 Discussion


















the next position



















20

18

16

14

12

10

08

06

04

02

Cap

Cap

Lowerboundary

Upperboundary

135

(s-a

)

05

(s-a

)

Crown 14 (s-a)N

orm

aliz

ed em

bank

men

t hei

ght

(s-a) Y (m)X (m)

ndash25ndash20

ndash15ndash10

ndash050

0510

1520

25 0005

1015

2025

3035






11138681113868111386811138681113868



⎧⎨

⎩ (5)







01

02

03

04

05

06

07



Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D








σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References























































































































































































































































Ra12 upi

1113944i

qsili + Apqp (2)





S ψsp 1113944

n1

i1

P0

ξEsi


+ 1113944

n2

in1+1

P0

Esi


(3)
























dz

Z

Pile

Ps

Pp

Ps

l0

l

σsz σsz


τfndash Um

Umτf+

τf+

τfndash

τ

τ

τf

ks

um

Z1

Z2

τ u

Transitionzone

Z ZZ

(I) (II) δb

δt

(a) (b) (c)

(e)

(d)

u

Elasticphase

Plastic phase


Surcharge load

Soil arching

Pile cap

Pile


fixed fulcrum


Geosynthetic






4 Discussion


















the next position



















20

18

16

14

12

10

08

06

04

02

Cap

Cap

Lowerboundary

Upperboundary

135

(s-a

)

05

(s-a

)

Crown 14 (s-a)N

orm

aliz

ed em

bank

men

t hei

ght

(s-a) Y (m)X (m)

ndash25ndash20

ndash15ndash10

ndash050

0510

1520

25 0005

1015

2025

3035






11138681113868111386811138681113868



⎧⎨

⎩ (5)







01

02

03

04

05

06

07



Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D








σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References


































































































































































































































































dz

Z

Pile

Ps

Pp

Ps

l0

l

σsz σsz


τfndash Um

Umτf+

τf+

τfndash

τ

τ

τf

ks

um

Z1

Z2

τ u

Transitionzone

Z ZZ

(I) (II) δb

δt

(a) (b) (c)

(e)

(d)

u

Elasticphase

Plastic phase


Surcharge load

Soil arching

Pile cap

Pile


fixed fulcrum


Geosynthetic






4 Discussion


















the next position



















20

18

16

14

12

10

08

06

04

02

Cap

Cap

Lowerboundary

Upperboundary

135

(s-a

)

05

(s-a

)

Crown 14 (s-a)N

orm

aliz

ed em

bank

men

t hei

ght

(s-a) Y (m)X (m)

ndash25ndash20

ndash15ndash10

ndash050

0510

1520

25 0005

1015

2025

3035






11138681113868111386811138681113868



⎧⎨

⎩ (5)







01

02

03

04

05

06

07



Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D








σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References

























































































































































































































































4 Discussion


















the next position



















20

18

16

14

12

10

08

06

04

02

Cap

Cap

Lowerboundary

Upperboundary

135

(s-a

)

05

(s-a

)

Crown 14 (s-a)N

orm

aliz

ed em

bank

men

t hei

ght

(s-a) Y (m)X (m)

ndash25ndash20

ndash15ndash10

ndash050

0510

1520

25 0005

1015

2025

3035






11138681113868111386811138681113868



⎧⎨

⎩ (5)







01

02

03

04

05

06

07



Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D








σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References

































































































































































































































































the next position



















20

18

16

14

12

10

08

06

04

02

Cap

Cap

Lowerboundary

Upperboundary

135

(s-a

)

05

(s-a

)

Crown 14 (s-a)N

orm

aliz

ed em

bank

men

t hei

ght

(s-a) Y (m)X (m)

ndash25ndash20

ndash15ndash10

ndash050

0510

1520

25 0005

1015

2025

3035






11138681113868111386811138681113868



⎧⎨

⎩ (5)







01

02

03

04

05

06

07



Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D








σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References

































































































































































































































































20

18

16

14

12

10

08

06

04

02

Cap

Cap

Lowerboundary

Upperboundary

135

(s-a

)

05

(s-a

)

Crown 14 (s-a)N

orm

aliz

ed em

bank

men

t hei

ght

(s-a) Y (m)X (m)

ndash25ndash20

ndash15ndash10

ndash050

0510

1520

25 0005

1015

2025

3035






11138681113868111386811138681113868



⎧⎨

⎩ (5)







01

02

03

04

05

06

07



Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D








σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References

























































































































































































































































11138681113868111386811138681113868



⎧⎨

⎩ (5)







01

02

03

04

05

06

07



Pile spacing s

Dep

th ra

tio o

f the

neu

tral

poi

nt (l

0l)

2D 3D 4D 5D 6D 7D 8D 9D








σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References



























































































































































































































































σsz

pm + cz( 1113857s2

minus N )

As

for zle l

pm + cz for zgt l

⎧⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎩

(7)










25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References



























































































































































































































































25

20

15

10

05

00



Nor

mal

ized

exca

vatio

n de

pth

(zD

)

0 25 50 75 100 125 150 175 200 225 250

P

P








Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References



























































































































































































































































Retainingwall

Foundation

Cushion

Pile

P

(a)

Walltranslation



Pile

Foundation

Cushion

P

(b)


1200

1300

1400

1500

1600

1700

1800



Aver

age s

tress

of t

he p

ile to

p (k

Pa)

60

65

70

75

80

85

90

95

100

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 10 20 30 40 50 60 70

(a)


1800

2000

2200

2400

2600

2800


40

50

60

70

80

90

Aver

age s

tress

of t

he so

il be

twee

n pi

les (

kPa)

0 2 4 6 8 10

Aver

age s

tress

of t

he p

ile to

p (k

Pa)

(b)







00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References


























































































































































































































































00 100 200 300 400 500 600 700 800 900 1000 1100 1200

2

4

6

8

10

12

14

Exca-3Exca-2Exca-1

Dep

th H

(m)

Axial force N (kN)

P









500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References


























































































































































































































































500

400

300

200

100

200 400 600 800 10000



Sliding surface



Dist

ance

from

the i

nner

side

of t

he b

ase p

late

(mm













6 Conclusions











Acknowledgments


References































































































































































































































































6 Conclusions











Acknowledgments


References




























































































































































































































































Acknowledgments


References






















































































































































































































































CFG Pile Composite Foundation: Its Engineering ...

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Transcript of CFG Pile Composite Foundation: Its Engineering ...