Axial Capacity of Driven Piles in Deltaic Soils Using CPT

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INVESTIGATIONS LTD.ELECTRIC CONE rENETRAT10N TESTINCAXIAL CAPACITY OF DRIVEN PILES IN DELTAIC SOILS USINGTHE OONE PENETRATION TESTByM.P. DaviesConeTec Investigations Ltd •• Burnaby. B.C •• CanadaP.K. Robertson, R.G. CampanellaUniversity of British Columbia, Vancouver, B.C., CanadaA. SyKlohn Leonoff Ltd., Richmond, B.C., Canada(preprint of paper to be presented at the)(First International Symposium on Penetration Testing, March 1988)

ABSTRACT: The prediction of axial pile capacity is a complex engineering problem.Traditional methods of data collection and subsequent analyses are frequently in errorwhen compared to full-scale load tests. Cone penetration testing (CPT) provides ameans by which continuous representative field data may be obtained.This paper compares the predictions fram thirteen axial pile capacity .ethods withthe results obtained from eight full-scale pile load tests on six different piles. Thepiles were steel pipe piles driven into deltaic soil deposits. The thirteen predictionmethods, separated into direct and indirect clasaes, used data obtained from the CPT asinput for analyses.A brief evaluation of each method investigated i. pre.ented and.the preferred.ethodCs) of analyses are identified.1 nmtODUCTIONThe continued growth of many large Canadianci~ies has led to increased construction oflarger more complex structures on sites withdifficult around conditions. In Vancouver.as in other metropolitan areas, large structuressuch as major highway bridae •• cementprocessing plants. storage tanka and hiahriseresidential and commercial complexe.are nov being constructed on deltaic andalluvial deposits. Essentially the deltaregion of the Fraser River is located immediatelyto the south of Vancouver. lbedelta region is covered by a thin veneer ofclays. silts and peats up to about 6 • inthickness. which is underlain by a tidalflatdeposit of sands and silt8 to a maximumthickness of 30 •• which in turn is underlainby stratified marine delta depositsrancing fram silty clays to clean sands upto 300 III in thickness. The groundwatertable is at or near the ground surface. Inthese Fraser River deltaic soil deposits.piled foundations are used extensively tosupport larae structures. The recent constructionof the Alex Fraser bridge andcorresponding highway extensions are excellentexamples. In order that a piled foundationmay be designed safely and economically.its behaviour under load must beaccurately predicted and ideally, a fullscalepile load test shoul~.be perfomed.Full-scale load tests are, however. veryexpensive and are therefore often impractical.Predictive methods for pile capacityrequire an accurate assessment of the propertiesof the· soil into which the pile isto be placed. The CPT o·ffers an excellentmeans to accurately obtain the requiredproperties, especially in aoft deltaicsoils.A total of thirteen static axial pilecapacity methods vere used to predict theresults obtained frOID eight full-scale pileload test. on aix 4ifferent piles. Thesemethods. aeparated into diTect and indirectclasses. used data obtained frCIII the conepenetration test (CPT). The CPT is a fast.economic and repeatable in-situ test. especiallyin loose and soft deltaic aediments.The CPT can also be considered to be a modeldisplacement pile.!his paper summari~es the results of theeiCht full-scale pile load tests and camparasthese results with the CPT predictionsusing the thirteen methods.2 TEST SITEThe test site is located on Lulu Islandwhich is within the post-glacial FraserRiver delta (Fig. 1). .The surficial geology of the Lulu Islandregion ia typical of a for.mer marine environmentno longer dominated by tidalaction. A summary of the 80il profile at

_.lS!U'• • •Fig. 1. General location of research site......IDE _,ie,~.~ ..__ ==~~ __ ~BD~ ~.~~ __ ~the test site to a depth of 75 m based ~nsampling and CPT is shovn in Fig. 2. Belowa surface layer of fill there is a prevalentdeposit of organic silty clays to a depth ofabout 15 JD that has been laid down in aquiescent swamp or marsh environment. Belowthis upper layer, a medium dense sanddeposit, locally silty. prevails to a depthof 30 m. This sand deposit is indicative ofa high energy depositional period and mostlikely represents a foromer channel bank ofthe Fraser River. Underlying the sand, to adepth of up to 150 to 200 m (Blunden. 1975).exists a normally consolidated clayey siltdeposit containing thin sand layers. Belowa depth of about 60 m the sand layers aremore prevalent and thiCker (up to 1 mthick) • The non-unifomty of the depositsbelow 30 m indicates a depOSitional historymost likely consisting of alternating turbulentand quiescent environments associatedwith either tidal flat facies. marginal bankor an alluvial floodplain depositional environment.The CPT profile in Fig. 2 presentsa clear picture of the stratigraphie detailat the test site •.. ltTI.IArID IJFn:IIEJfTIAL P.P.'f II) IrAflO 'u/qt11-..... - ........... - .2 0.' - SAND FILLSoftorvonicsilty CLAYMediumadense SAND:z:~C1..WC!ItNonnollyconsolidatedclore,SILTwith thinsend Joy.r.Soft,normoll,consolidatedcloyey SILTwith SANDloyersFig. 2.Soil profile for pile research site. (1 bar • 100 kPa)

Aeross the entire site. 2 to 4 m of nonhomogeneousfill exists at the surface. Forthe purpose of facilitating in-situ testing,making pile driving possible. and stuayinglateral pile behaviour, the fill materialvas removed in the general area of theresearch piles. This material vas replacedwith clean sand. -Six pipe piles vere driven (four 324 mmdia •• 9.5 mm wall thickness; one 324 mmdia •• 11.5 mm thickness. one 915 mm dia ••19 mm thickness) at the site. The relativeembedments and pile tip conditions of thepiles are shown in Fig. 3. The five smallerpiles were placed and tested under thesupervision of University of British Columbia(UBC) personnel. The large pile vasplaced and tested under the supervision ofthe B.C. Ministry of Transportation andHighways (HOTH). Pile No.1 had a largerdiameter sleeve for the first 2 m to removeany frictional resistance in the upper sandfill (see Fig. 3).3 AXIAL PILE LOAD 'l'ESTSapplied in roughly 5% increments of theanticipated failure load for the piles shownin Fig. 3. The 'Quick Load ~est Method' v'used to minimize time-dependent effects.summary of the pile driving and testingscheaule is presented in ~able 1.Table 1. UBC/HOliJ pile driving and testingschedules.PileI Pile Driving TestingTest Length Date(s} Date(s)No. (m)1 14.3 19 AUG 85 09 NOV 852 13.7 16 AUG 85 01 MAR 853 16.8 16 AUG 85 09 NOV 854 23.2 16 AUG 85 01 !Wt 855 31.1 15 AUG 85; 22 SEl' as:16 AUG 85 06 OCT 85A 67.0 10.11.13 .16. 09 HAY 8417 APR 84B 78.0 11 HAY 84 01 JUN 84C 94.0 09 JUN·84 29 JUN 84The 'Quick Load Test Method' of axialloadina

Analysis of the results from axiallyloaded vertical test piles is more complicatedthan generally realized (Brierley etaI, 1978). For a pile (generally assumed tobe stronger than the soil), the ultimate,failure load is reached when the pileplunges; i.e., rapid settlement occprs undersustained or only slightly increased load.This definition. however. "is often inadequatebecause plunging requires very largedisplacements and is often less a functionof the pile-soil system and more a functionof the capacity of the man-pump system(Fellenius, 1980). To be useful. a failuredefinition should be based on a simplemathematical rule that can generate repeatableresults independent of the individualusing the method and of the seale ehosen forplotting the load test data. For example.Fig. 4 shows the results of a hypotheticalpile load test plotted to different scales.The hypothetical test pile could be interpreted.based on a visual inspection of theresults. as a predominantly friction or'floating'. pile (upper figure) or a predominantlyend bearing pile Clower figure).A popular method of interpreting axial pileload test data is that by Daviason (197])and involves a simple araphieal manipulation-0.5-Eu1.0z0~ - 1.5(,)IU..J~WQ2.0Q. 2.50t-IU 3.0..J- Q."3.54.000LOA 0 (kN)200 400 600 800 1000 12000Eis2.04,0Fig. 4. Load-displacement diagram of hypotheticaltest pile drawn to two differentseales.of the theoretical elastic compression linefor the pile in question. Davisson's method(1973) has been used in this study to determinefailure loads. Fel1enius (1980)studied nine commonly used failure criteriaand found Davisson'S method to be among themost conservative.Fig. 5(a) presents a summary of the loaddisplacementtest results for the fivesmaller piles. Based on the telltale datapiles 1, 2 and S are interpreted as predomdnantlyshaft resistance piles whereaspiles 3 and 4 had significantly larger contributionsto their total capacity from endbearing. Pile No. 4 could not be loaded tofailure. but the load-deflection diagram wasbased on the combined results of the otherpile test results. Fig.SCb) presents asummary of the load-displacement results forthe larger pile. The larger pile was testedat three depths (67. 78 and 94 m) as shownin Fig. 3. All three test results (Fig. 5b)indicate that the larger pile bas a largeshaft resistance component. The ~eductionin measured load observed for the largerpile at 67 m and 94 m depth occurredbecause, with rapid axial deflections. thehydraulic jacks were unable to sustain theload. Full details of the test program forthe 915 mm pile is given by Robertson et al(1985). A summary of the axial load testingis presented in Table 2.Table 2. Full details of the overall testprogram are given by Davies (1987).Wall Openl Capaci-PileI Length Dia- Thick-. Closed ty (leN)Test meter 'ness LID Ended CDavis-No. (m) (m) (DID) son.1973}1 14.3 0.324 9.5 44 C 1702 13.7 0.324 9.S 42 C 2203 16.8 0.324 9.5 52 C 6104 23.2 0.324 9.5 72 0 12005 31.1 0.324 11.5 96 C 1070A 67.0 0.915 19 73 0 7500B 78.0 0.915 19 85 0 7000C 94.0 0.915 19 103 0 80004 PREDlCTION OF STATlC AXIAL PILE CAPACITY!he prediction methods will be separated asfollows:1) direct methods2) indirect methods.The term "direct method" is applied to anystatie predietion method that uses CPT data(tip resistance. q~. and/or sleeve friction,

EAXIAL LOA 0 (kN»00~.,~~~4~0~0~;;1~00~:?·90~0~ __ ~~~Z "o ,;: ~~ ./' '~=' 20 . -.-. f._ ,r----.---...l_ ..... e; ..._ ..'\~ 2S of~o~ 30III= 35~- zoe: 30~. 40~~ soIIIC 50~o 70t-III 10:90&100,~I •• t.Z.3 .5,(0) use PILE RESEARCH SITEAXIAL LOAD TEST RESULTSTEST C ot t4fttTEST 8 Of T8.. TEST A Of 17 ..LEGEND'I c.,.eit,t ,0. ..... " 1,'13 J\Itia. .... 1 \\\(bJ MOTH PILE RESEARCH SITEFig. S. S1mIII&ry of axial load test re.ul U.f" depending upon -method used) directly bythe use of theoretical and/or empiricalscaling factors without the need to evaluateany intermediate values (coefficients ofearth pressure, bearing capacity factors,friction angle, etc.). The scaling factors,in all cases, resemble the original work ofde Beer (1963). De Beer (1963) suggestedthat if a probe of zero diameter penetratesa soil layer, the device would "feel" theentire effect of the lover soil layer iDaediatelyupon penetratiOn. However, if alarge diameter pile vere pushed into thelayer, the point resistance would not equalthat of the zero diameter probe until thepile reached a greater depth. This depth isoften termed the critical depth. De Beershowed that it i. reasonable to assume thatthe pile resistance curve between the layerinterface and the critical depth varieslinearly; thus, the pile resistance at anyintermediate depth could be determined ifboth the idealized penetration resistancecurve and the critical depth were known.Although it is not possible to use a probeof zero diameter, the standard electric~\cones (35.7 DID in diameter) can be assumedto approximate this condition, especiallyfor large diameter piles. This concept iscomplicated in highly layered materialsTable 3.Prediction methods evaluatedDirect lIethods References Notes1. Schmertmann Schmertmann Proven CPTand Notting- (1978)~ethodham CPTCc'c & f. used)2. de Ruiter de Ruiter Europeanand Jeringen and Beringen (Fugro)CPT (1979) (qc & fs used)3. Zhou et a1CPTZhou et al(1982)Chinese iailwayExperiencee Cic: & fa used)4. Van Hierlo Van !!ierlo Original Dutchand lCoppejan and Koppejan (C;c only used)CPT (1952) and .Begemann etal (1982)5. Laboratoire LCPC-Busta- French HethodCentral mante and (C;c only used)des Ponts et Gianesa1liChaussees (1982)CPT (LefC)6. Belgian CPT W .F. Van Impe Belgian Method(1986) (C;c only used)Indirect Methods References Notes7. All RP2A American OffshorePet. Inst.(1980)8. Dennis and Dennia and Modified AlIIOlson Olson(1983a &. b)9. Vijayvergiya Vijayvergiya "A"Hethodand Focht and Focht(1972)10. Burland Burland(1983)ll. JanbuJanbu (1976) NIT12. Heyerhof Heyerhof OriginalConventional (1976) BearingTheory13. Flaate andSeInesFlaate andSelnes(1977)NGI

\\ • pu. No.Svhere layer thicknesses are less than the Host pile prediction methods are relativelydifficult and time consuming to implementcritical depth for the large diameter pile.In these situations the full penetration without the aid of a computer. This isresistance may be mobilized on the cone but especially true when near'continuous CPTmay not be realized for the pile before the data is used. For each of the predictioninfluence of another layer is felt. The way' methods used in this study a computerin which the different direct methods define program was written using commerciallythe critical depth and layering effects for available spreadsheet software. The spreadsheetis seen as a powerful engineeringboth sleeve friction and point resistanceis. for the most part. what separates the computational tool that is veIl suited tomethods available.geotechnical engineering design. TheAn "indirect method" is taken to refer to spreadsheet is particularly well adapted forstatic prediction methods that require perfor.ming sensitivity analyses and thereforerapid evaluation of input parameters.intermediate correlations in order to pre-­dict pile capacity from CFT data. It must Perhaps the greatest attraction of usingbe realized that. unlike the direct methods. spreadsheets. however. is that the programmer/operatorrequires little computermost indirect methods were not formulatedspecifically for use with CFT data. As programming background.such. any discrepancies between the predictedand measured pile capacities using capacities for one of the direct and one ofExamples of predicted and measured pilethe indirect methods may not be due 801e1y the indirect methods are shown in Figs. 6to problems inherent to these methods. and 7. respectively. Fig. 6 shows the LCPCTable 3 lists the thirteen predictive CFT (French) method and Fig. 7 shows themethods evaluated. The first six methods Dennis and Olson (modified API) method.are direct methods whereas the remaining Note that the LCPC method predicts theseven are indirect methods. In each case capacity of both the smaller piles and thethe CPT data used was that shown in Fig. 2. tests on the larger pile with excellent30PREDICTED PILE CAPACITY (kN)PREDICTED PILE CAPACITY (kN)o 500 1000 1500 2000 2500 00 5000 10000 15000 20000 25000o~~~----~--~----~--~510USC PILESMOTH PILE324mm diameter91!Smm diameterSteel pipe pile.St.el pip. pile15E\%:\..- 20 '\~ 50CLa.J&IJ \Q0 \25 .60""'.\708035 \Short Reliitonci• 90Totol R •• latonce40 100USC PILE RESEARCH SITELCPC CPT MethodMOTH PILE RESEARCH SITELCPC CPT MethodFig. 6._~lo, ... ~Predicted axial capacity vs. depth for UBC and MOTH pile test sites using LCPC

agreement. The Dennis and Olson methodpredicts the capacities of the smaller pilesquite veIl but significantly overpredictsthe capacities of the tests on the largerpile. This trend is seen for all of theindirect methods evaluated. Results forpile 1 are not included in Figs. 6 and 7because the predicted pile capaciti~s showninclude the resistance in the upper" sandfill vhich vas not acting on pile 1. Topredict the capacity of the 915 mm diameterpile at depths greater than 75 m the CPTprofile vas projected assuming a continuedlinear increase (see Fig. 2). Availableborehole data to a depth of 130 m suggeststhis is a reasonable assumption.Fig. 8 summarizes the results of all themethods in the form of bar charts. Forreasons mentioned previously. the resultsfor pile No.1 are not included. Note thatboth the direct and indirect methods providedreasonable predictions of the measuredcapacities of the smaller piles. The directmethods, the Zhou et al method to a lesserextent, also predicted the capacity on thelarger pile quite satisfactorily. Hovever,wi thout exception. the indirect methods hadpredictions that were significantly in errorand non-conservative when compared to themeasured results for the large pile. Sincethe indirect methods generally did reasonablywell in predicting the capacity of thesmaller piles. and since the piles are allin the same deltaic soil deposits, theresults suggest that scale effects areextremely important for the large diameterpile. Host of the indirect methods areempirical in nature and based upon observedresults from piles considerably smaller than915 DID in diameter and 100 m in length.5 SUMMARY AND CONCLUSIONSThis paper briefly compares thirteen axialpile capacity methods with the results fromeight full-scale pile load tests on sixdifferent piles. The piles were steel pipepiles driven into deltaic soil deposits.The length to diameter ratios (LID) for thepiles ranged from 40 to 100. The measuredaxial capacities ranged from 170 kN to B,OOOleN in soils that included organic silt. sandand clay.PREDICTED PILE CAPACITY (kN)0°p-~~~0~0 __ ~IOTO~0~1~5rO~0~2_0~0_0_2_~~OOPREDICTED PIL.E CAPACITY (kN)00 ~OOO 10000 15000 20000 25000MOTH PILE91!5mm diameterSteel pipe pile\Tnt A •..T.a, a.T ••• c.\.\ .., \\~Oj.C'.d\, ,\, \\ \\ \, "MOTH PILE RESEARCH SITEDennis and Olson MethodFig. 7. Predicted axial capacity vs. depth for UBC and HOTH pile test sites usingDennis and Olson method.

. t..i.c. ••r •10I: c. II ••f ,•i":• •c•i I• 1f.r .' ..:c • •. II I;.·,i·•I: c... thod 1: Sell_r'IIIO"" ."CS ".U;",holll C'T•••• ,C, •••• ' ••• II,. c ••• el". c.,o 10 .. eo 10 coo 120 '.0 .. 0 '00 100I IIIIII;IIIIIi!-••n'00" MliS121A" •• t~.%".,hod 2: ,. R.iter 0'" .eri",e" e,Sf·• 1I1.,C".,II •• I.,. •• C ••• CI' ....,o 10 .. eo , 00 100 110 •• 0 .00 '10 100..5%....4'SI100.os...10 ... ,0'''' "·14%".thod 3: ZIIo."Zie,Zo.,Lo •• " .. To ... C'T••• D'CT,.'III",.,II,. C".IoC"" c.,-,.io 10 .. eo eo 100· IZO MO '.0 .00 100 "...I11.0,'15I.nI.III.. ,.".,ItlAwe. 140% S'. 34%".tllod ~: Vo" Mierlo 1"11 Ieo ... jo" CPT• II'.ICT,.'III.,UII,. C .... C"" c.,0 ao 40 10 eo 100 ItO 140 .. 0 110 ~pc'"I.,IInI101:.,.ITSIII ,. "A .....,. U·21%"Itllod 15: LC,e C'T••'.ICT,.'II,.,U_,. CIo •• CIT" coa,o 10 .. 00 .0 '00 110 MO '10 '00 100 . "II"I'ISI •• I.,00II•.0s'0.10",-100% ".IS%..II'.'CTI.'III .. IIIII. clo •• cn" c~,o 10 .. 10 eo 100 lao '.0 110 '10 100 or.1..,T I"I 111,"I101110'.0Fig. B. Summary of predicted va. measuredaxial pile capacity."othod 7: API 111'210•••• ICT ••,..".UII,. C ••• C'T. '"o • .0 10 III , .00 110 '.0 .10 ••,0 100.I sII,;.. .i·•I: co.I: s.. "i·:c •••:a..•• •~.i •• I•cI!i15lSIliS...IS.UllIn"otllod I: D.""i. 0'" 01 ••" A ••·'51" SI.&2".••• I'CT'.'II,Io •••,. CIo.IoC"" c ••o 10 .0 , .. 10 .00 110 '.0 '.0 .eo 100 '"II,II51III1111141104"...I""·'27" U •• 3%.".tllod,: Ylto, ••"I,1 Oft, '~I••••,CT'.'II'•• UII,. C ••• CITY ,

CPT data was used for the prediction ofpile capacity for the thirteen methods evaluated.The direct methods, which incorporateCPT-pile scaling factors, providedthe best predictions for the piles andmethods evaluated. Based on the results ofthis study the following three directmethods are preferred: .1. LCPC CPT (Bustamante and Gianesalli,1982)2. de Ruiter and Beringen CPT (1979)3. Schmertmann and Nottingham CPT (1978)For the piles tested, the LCPC (French)method is shown to be the best method vi th amaximum error of about 2S1, an average errorof 01. and a standard deviation (Sd) of 151.In addition, the LCPC does not directlyrequire the CPT sleeve friction value otherthan to define soil type. "l'his is adesirable feature since ~he cone bearing isgenerally obtained with more accuracy andconfidence than the sleeve friction.When piles are required to be supported insoft deltaic soils the CPT can be a highlyeconomical.method of providing extensivesubsurface information to predict axial pilecapacity.The results of this study indicate thatindirect CPT methods to predict axial pilecapacity =ay significantly overpredict thecapacity of large diameter. long piles (LID> 75) supported in soft clayey soils.The assistance of the NAtural Sciences andEngineering Research Council of Canada;lOohn Leonoff. Richmond: British ColmllbiaMinistry of Transportation and Highways, inparticular Mr. Don Fraser: Franki Canada,Richmond: members of the USC In-SituTesting Group, and the technical staff ofthe Civil Engineering Department, Universityof British Columbia, is very much appreciated.American Petroleum Institute (1980), "RecommendedPractice for Planning, Designing,and Constructing Fixed Offshore Platforms.API RP lA. 11th edition.Begemann, B.K.S.Ph., Joustra, K., Te Kamp,W.G.B •• Krajicek, P.V.F.S., Heijnen, W.J.,and Van Weele. A.F. (1982), Cone PenetrationTesting. Civiele & Bouwkundige Teehniek.No.3. The Netherlands.Blunden, R.B. (1975), "Urban Geology ofRichmond, British Columbia." Adventures inEarth Sciences Series No. 15, B.C. Govt.Publications.Brierley. G.S., Thompson. D.E., and Eller,C.W. (1979). "Interpreting End- BearingPile Load Test Results," Behaviour of DeepFoundations, AS!H S'l'P 670. RaymondLundgren. Ed •• American Society forTesting and Haterials. pp. 181-198.Burland, J.B. (1973). "Shaft Friction ofPiles in Clay - A Simple FundamentalApproach." Ground Engineering. Vol. 6. No.3, pp. 30-42.Bustamante, M. and Gianeselli, L. (1982)."Pile Bearing Capacity Prediction by meansof .Static Penetrometer CPT." PenetrationTesting. ESOP'! II, Amsterdam, Vol. 2, pp.493-500.Davies, M. (1987). "Predicting Axially andLaterally Loaded Pile Behaviour UsingIn-situ Testing Methods." M.A.Sc. thesis.Civil Engineering Dept., University ofBritish Columbia, Vancouver, B.C.Davisson, M.T. (1973). "High CapacityPiles," Proceedings. Lecture Series, Innovationsin Foundation Construction. ASCI.Illinois Section, Chicago, 52 pp.de Beer, E.E. (1963), "The Seale Effect inTransportation of the Results of Deep. Sounding Tests on the Ultimate Bearingcapaci ty of Piles and caisson Foundations,"Geoteehnique. Vol. 8, p. 39.Dennis, N.D. and Olson. R.E. (1983a), "Axialcapacity of Steel Pipe Piles in Clay," Am.Soc. of Civil Ingrs., Geo~eehnical Practicein Offshore Engineering. Austin, pp.370-387.Dennis, N.D. and Olson, R.E. (l983b), "Axialcapacity of Steel Pipe Piles in Sand," Am.Soc. of Civil Ingrs., Geotechnical Practicein Offshore Engineering, Austin, pp.389-402.de Ruiter, J. and Beringen. F.L. (1979),"Pile Foundations for Large North SeaStructures," Marine Geoteehnology. Vol. 3.No.4. pp. 267-314.Fellenius, B.B. (1980), "The Analysis ofResults from Routine Pile Test Loading."Ground Engineering, Foundation PublicationsLtd., London, Vol. 13, No.6, pp.19-31.Flaate, K., and SeInes, P. (1977), "SideFriction of Piles in Clay, "Proceedings ofNinth International Conference on SoilMechanics and Foundation Engineering.Tokyo, Japan. Vol. 1, pp. 517-522.Janbu, N.· (1976), "Static Bearing Capacityof Friction Piles," Proceedings of theEuropean Conference on Soil Mechanics andFoundation Engineering, Vol. 1.2, pp.479-488.Meyerhof. G.G. (1951), "The Ultimate Bearingcapacity of Foundations," Geoteehnique,Vol. 2. No.4, p. 301.

Meyerhof, G.G. (1976), "Bearing Capacity andSettlement of Pile Foundations," ASCEJournal of Geotechnical EngineeringDivision. Vol. 102. No. GT3. pp. 197-228.Robertson. P.K. Campanella. R.G •• Brown.P.T., Graf, I •• and Hughes, J.H.O. (1985),"Design of Axially and Laterally-LoadedPiles Using Insitu Tests: A Case History,"Canadian Geotechnical Journal. Vol.22. No.4. pp. 518-527.Schmertmann. J.H. (1978). "Guidelines forCone Penetration Test. Perfor.mance andDesign." Federal Highway Administration.Report FBWA-TS-78-209. Washington. July1978. 145 pp.Van Impe. W.F. (1986), "Evaluation of Deformationand Bearing Capacity Parameters ofFoundations from Static CPT-Results,"Fourth International Geotechnical Seminaron Field Instrumentation and In-SituTesting. 25-27 November. 1986. Singapore.pp. 1-20.Van Hiarlo, W.C. and Koppejan. A.W. (1952>,"lenita en Draagver.mogen van Beipalen."BoUY. 19 Jan. 1952.Vijayvergiya. V.A. and Focht. J.A •• "A NewWay to Predict Capacity of Piles inClays." Proceedings of Fourth OffshoreTechnology Conference, Houston. Vol. 2,pp. 865-874.%bou. J., Xie. Y., Zuo. Z.S., Luo, H.Y. andTang, X.J. (1982), "Prediction of LimitLoad of Driven Pile by CPT." PenetrationTesting. Proc. 2nd European Symp. PenetrationTesting. ESOPT II. Amsterdam, Vol. 2.pp •. 957-961.-,