Design and construction of a deep excavation in so

DesignandconstructionofadeepexcavationinsoftsoilsadjacenttotheShanghaiMetrotunnelsZ.F.Hu,Z.Q.Yue,J.Zhou,andL.G.ThamAbstract:Thispaperpresentsthedesignandconstructionofadeepexcavationforbuildingfoundationsinsaturatedsoil.ThisdeepexcavationwasofparticularinterestbecauseitwaslocatedaboveandbesidetheShanghaiMetrotun-nels.ThetwinShanghaiMetrotunnelshadtobeinfulloperationduringthedeepexcavation.Potentiallargedeforma-tionofthetwintunnelswasoneofthemainconcernsduringthedesignandconstructionforthedeepexcavation.Thepaperdiscussesindetailthecriteriaandmeasuresforcontrollingthesoilandtunneldeformation.Themeasuresin-cludedcast-in-placeconcretediaphragmwallswithbracingstructuralmembers,pumpingconsolidation,cement–soilmixpilesystems,andrationalexcavationprocedures.Asimplifiedtheoreticalmethodwasproposedtoestimatethein-crementinundrainedshearstrengthinasoftclaylayerduetopumpingconsolidation.Furthermore,conventionalfiniteelementmethodswereusedtopredictthesoilverticalandhorizontaldisplacementsinducedbytheexcavation.Usingthedesignandconstructionmethodsdiscussedinthepaper,thesettlementandhorizontaldisplacementofthetunnelsweresuccessfullycontrolledwithin5.0mmand9.0mm,respectively.Thecurvatureoflongitudinaldeformationcurveofthetunnelswaslessthan1/15000.Thehorizontaldisplacementofthebraceddiaphragmwallswaslessthan0.12%ofthetotalexcavationdepth.Keywords:Metrotunnels,saturatedsoftsoil,deepexcavation,design,construction,groundimprovement,casestudies.Résumé:Cetarticleprésentelaconceptionetlaconstructiond’uneexcavationprofondepourlaconstructiondefon-dationsdansdessolssaturésmous.Cettefondationprofondeétaitparticulièreencequ’elleétaitsituéeau-dessusetàcôtédestunnelsdumétrodeShanghai.Lestunnelsdumétrosontjumelésetdevaientresterenopérationcontinuelledurantlestravauxpourl’excavationprofonde.Unedéformationpotentiellementimportantedestunnelsjumelésconsti-tuaitunedesprincipalespréoccupationslorsdelaconceptionetdelaconstructiondel’excavationprofonde.Cetarticlediscuteendétaillescritèresetdesmesuresprisespourcontrôlerlesoletladéformationdestunnels.Lesmesurescomportaientdesparoismouléesenbétonavecdesmembruresdecontreventement,delaconsolidationparpompage,dessystèmesdepieuxmixesdesol–cimentetdesprocéduresrationnellesd’excavation.Onaproposéuneméthodethéoriquesimplifiéepourestimerl’accroissementdelarésistanceaucisaillementdanslacouched’argilemolledûàlaconsolidationparpompage.Deplus,onautilisédesméthodesd’élémentsfinisconventionnellespourprédirelesdépla-cementshorizontauxetverticauxdusolinduitsparl’excavation.Enutilisantlesméthodesdeconceptionetdecons-tructiondiscutéesdanscetarticle,letassementetledéplacementhorizontaldestunnelsontétécontrôlésavecsuccèsàmoinsde5,0mmet9,0mmrespectivement.Lacourburedelacourbededéformationlongitudinaledestunnelsétaitinférieureà1/15000.Ladéformationhorizontaledelaparoimouléeétayéeétaitinférieureà0.12%delaprofondeurtotaledel’excavation.Motsclés:tunnelsdemétro,solmousaturé,excavationprofonde,conception,construction,améliorationduterrain,étudesdecas.[TraduitparlaRédaction]Huetal.9481.IntroductionShanghaiisoneofthelargestandmostwell-knowncitiesinChinaandaroundtheworld.Shanghaihasapopulationexceeding13millionandamunicipalareaofabout6340km2.Withtherapideconomicdevelopmentandreformofthelasttwodecades,Shanghaihasbeengraduallyregain-ingitsreputationasaninternationaleconomic,financial,commercial,andindustrialcenter.Accordingly,constructionactivitiesofcivilinfrastructuresandbuildingsintheMunici-palityofShanghaihavebeenincreasingsignificantly.Theintentionofthispaperistointroduceoneoftheseactivities,namelythedesignandconstructionofadeepexcavationforacommercialbuildinglocatedcloselyaboveandbesidetheShanghaiMetrotunnel1.2.Background2.1.ShanghaiMetrotunnelsShanghaiMetroline1,asoneofthemaincomponentsofthemunicipaltransportationnetwork,islocatedinthedown-Can.Geotech.J.40:933–948(2003)doi:10.1139/T03-041©2003NRCCanada933Received5February2002.Accepted1May2003.PublishedontheNRCResearchPressWebsiteat’sRepublicofChina.Z.Q.Yue1andL.G.Tham.DepartmentofCivilEngineering,TheUniversityofHongKong,PokfulamRoad,HongKong,People’sRepublicofChina.1Correspondingauthor(e-mail:[e-mail]).I:\cgj\CGJ40-05\T03-041.vpSeptember12,20031:33:21PMColorprofile:DisabledCompositeDefaultscreentownareaofShanghai,anareawithadensenetworkofbuildings,roads,streets,andurbaninfrastructure,asshowninFig.1.Metroline1runsnorthandsouthandcarriesaverylargenumberofpassengerseveryday.Metroline1wasconstructedbetween1990and1994andcommencedoperationinApril1995.Anextensionofthelineinthesouthendwascompletedin1997.Atpresent,ShanghaiMetroline2isbeingconstructedandrunsfromeasttowest(seeFig.1).Metroline1has16stationsandatotallengthof21.615km,whichcomprisesan18.620kmlongunder-groundtunnelanda2.995kmlongabovegroundsectionoftrack.Theundergroundtunnelshavetwodifferentcrosssec-tions,namelycircularandrectangular.Thetunnelswithacircularcrosssectionwerefabricatedwithsi