Load Testing of Rock Socket Pile in Downtown Calgary, Alberta – A Case Study

Deepak Kumar, Joseph Yonan

In the proceedings of: GeoOttawa 2017: 70th Canadian Geotechnical Conference; 12th joint with IAH-CNC

Session: Piles I

ABSTRACT: TheconstructionofCalgary™sNewCentralLibraryindowntownCalgary,Alberta,overanexistingat-gradeLightRailTransit(LRT)linerequiredadeepfoundationsystem.TheprojectlocationimposedtheneedforconstructionofanencapsulationstructurespanningovertheLRTlineandsubsequentconstructionofthelibrarybuilding,aboveandadjacenttotheencapsulationstructure.Thefoundationoftheencapsulationstructurerequiredhighloadcapacities,owingtotherelativelylargespanoftheencapsulationstructure.Consideringthehighfoundationloads,adeepfoundationsystemconsistingofboredcast-in-placepilessocketedinthebedrockwaschosentosupporttheencapsulationandthebuildingstructures.AnOsterbergCellpileloadtestwasundertakenonatestpilefoundedinbedrocktoestimateandoptimizethefoundationdesign.Baseandshaftresistanceparametersforthefoundationdesignwereestimatedseparatelyfromtheresultsoftheloadtest.Costsavingsandexpeditionoftheconstructionschedulewereachievedthroughthepileloadtestanddesignoptimization.Thispaperpresentstheresultsofthepileloadtestandacomparisonofestimatedpiledesignparameterswiththosepredictedusinganalyticalmethodsandwiththosepresentedinsimilarpreviousstudies.RÉSUMÉLaconstructiondelanouvellebibliothèquecentrale,NewCentralLibrary,aucentre-villedeCalgaryaudessusd™uneligneexistantedumétroléger,LightRailTransit(LRT)nécéssitaitunsystèmedofoundationprofonde.L™endroitduprojetexigeaitlaconstructiond™unestructured™encapsulations™étendantau-delàdelaligneLRTetlaconstructionsuivantedelabibliothèqueaudessusetauprèsdelastructured™encapsulation.Lafondationdelastructured™encapsulationexigeaitdescapacitésdechargesélevées,àcausedelagrandeurdelastructured™encapsulation.Enconsidérationdeschargesélevéesdelafoundation,unefondationprofondecomposéedepieuxforésmoulésenplacedanslesubstratrocheuxaétéchoisiepoursoutenirl™encapsulationetlesstructuresdubâtiment.UnessaidechargedepileOsterbergCellaétéréalisésurunepileéchantillondanslesubstratumrocheux,pourestimeretoptimiserleplandelafondation.Lesparamètresderésistancedebaseetarbrepourleplandelafondationontétéestiméesséparément,d™aprèslesrésultatsdel™essaidecharge.L™essaidechargedepileetl™optimisationduplanontréduitlescoûtsetonthâtélaconstruction.Cetarticleprésentelesrésultatsdel™essaidechargedepileetunecomparaisondesparamètresduplandepileestiméeàceuxpréditavecdesméthodesanalytiquesetaveccellesquifigurentdanslesétudesprécédentssimilaires.1INTRODUCTIONPileloadtestsaregenerallyconductedtobetterestimatethepiledesignparameters,understandtheconstructionchallenges,optimizetheprojectcost,andtobeabletousehighergeotechnicalresistancefactorsinthelimitstatesdesignmethodology.TheCanadianHighwayBridgeDesignCode2014allowstheuseofhigherresistancefactorsof0.6whendesignparametersareestimatedusingstaticloadtestforcompressiveloads.WithanOsterbergCell(O-Cell),pileloadtestondeeppilescanbeconductedeconomically,comparedtotheconventionaltestingmethod.Theconventionalmethodgenerallyrequirestheuseofreactionpiles,whicharenotneededwhenusingtheO-Cellmethod.GiventhattheO-CellgenerallyutilizesreactionfromshaftresistanceabovetheO-CellandendbearingbelowtheO-Cell,testingashorterpileusingO-Cellmightnotprovideallthedesireddesignparameters.Mobilizingtheultimateshaftandthebaseresistancessimultaneouslyinasingleloadtestmayormaynotbefeasible,andgenerallydependsonthelocationoftheO-Cell.Withtheaboveconsideration,thelocationoftheO-Celliscriticalforobtainingoptimumresults.ThispaperpresentsacasestudyofapileloadtestconductedusinganO-CellatthesiteofCalgary™sNewCentralLibrary.Piledesignparametersestimatedfromtheloadtesthavealsobeencomparedwiththoseestimatedfromanalyticalmethods.2BACKGROUNDThisloadtestwasconductedduringthefoundationdesignofCalgary™sNewCentralLibrary,locatedinareastotheeastof3Streetandbetween7Avenueand9AvenueinsoutheastCalgary,Alberta(Figure1).Thefive-storeybuildingstructurewithnobasementrequiredcolumnswithfactoredloadsofupto25,000kN.Intotal,theprojectrequiredinstallationofmorethan150boredcast-in-placeconcretepilesfoundedinthebedrock.Consideringthenumberofpilesandtheirdesignloads,onepileloadtestwasconductedtoobtainamoreaccurateestimateofpiledesignparameters,aswellasto

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