香港理工大学殷建华老师之市公开课金奖市赛课一等奖课件

深基坑开挖与支护设计

殷建华TheDepartmentofCivil&StructuralEngineeringTheHongKongPolytechnicUniversity,HongKong,China1第1页OutlineofLecturesbyJHYIN:Lecture1:SubsoilExploration(Chapter2-Das)Lecture2: ShallowFoundations(Chapter3-Das)Lecture3: MatFoundations(Chapter4-Das)Lecture4: LateralEarthPressureandRetainingWalls(Chapter5-Das)Lecture5: SheetPileWalls(Chapter6-Das)Lecture6: BracedCuts(Chapter7-Das)Lecture7: PileFoundations(Chapter8-Das)Lecture8: SoilImprovementandGroundModification(Chapter11-Dasplusothers)EssentialReferences:Das,BrajaM.().PrinciplesofFoundationEngineering(6thedition),Thomson,UnitedStates(ISBN0-534-40752-8)2第2页6.1Introduction6.2ConstructionMethods(施工方法)6.3CantileverSheetPileWalls（悬臂板桩墙）6.4CantileverSheetPilingPenetratingSandySoils6.5CantileverSheetPilingPenetratingClay6.6AnchoredSheetWalls6.7FreeEarthSupportMethodforPenetrationofSandySoil6.8MomentReductionforAnchoredSheetPileWalls6.9FreeEarthSupportMethodforPenetrationofClayLecture6:SheetPileWalls(Chapter6-Das)板樁墻3第3页6.10Anchors6.11UltimateResistanceofAnchorPlatesandBeamsinSand（锚板和锚梁极限承载力）6.12UltimateResistanceofAnchorPlatesandBeamsinClay(fu=0condition)6.13FactorSafetyforAnchorPlatesandBeamsLecture6:SheetPileWalls(Chapter6-Das)板樁墻4第4页6.1IntroductionPurposes:

supportingexcavation,retainingsoil,stoppingwaterinflow,…支撑开挖，挡土，阻止水渗流5第5页Diaphragmwallsareundergroundstructuralelementscommonlyusedforretentionsystems,permanentfoundationwalls,deepgroundwaterbarriers.地下连续墙普遍用于支撑体系，永久性基础外墙，挡水地下结构体。Diaphragmwallsareconstructedusingtheslurrytrenchtechnique,whichwasdevelopedinEuropeandhasbeenusedinHongKongsincethe1970‘s.地下连续墙施工过程中采取了泥浆护壁。Thetechniqueinvolvesexcavatinganarrowtrenchthatiskeptfullofanengineeredfluidorslurry.泥浆护壁技术是开挖窄槽..Theslurryexertshydraulicpressureagainstthetrenchwallsandactsasshoringtopreventcollapse.泥浆给窄槽壁施加水压，预防坍塌Slurrytrenchexcavationscanbeconstructedinalltypesofsoil,evenbelowthegroundwatertable.泥浆护壁沟渠开挖适合用于各种土层Diaphragmwalls（地下连续墙）:6第6页BentoniteSlurry（工程中配置泥浆原理图）7第7页3-DViewofDiaphragmWallConstruction8第8页9第9页Woodensheetpileandconcretesheetpile（木板桩，混凝土板桩）:10第10页Steelsheetpile(usedalotinHongKong):11第11页SteelsheetpilesfromJapanandUKareoftenusedinHongKong.

BelowisfromUSA.12第12页13第13页6.2ConstructionMethods(后填土支护施工过程)14第14页15第15页6.3CantileverSheetPileWalls（悬臂板桩墙，实际变形、受力图）Rotationpoint:Howtofindit?旋转点？16第16页FromSoilMechanicsbyCraig()(7thEdition)两种力学模型Fixedearth(bendinghere)Freeearth(nobendinghere)(simpleandgood)17第17页6.4CantileverSheetPilingPenetratingSandySoilsFixedearthmethod(bendinghere)18第18页Purpose:TodesignD（入土深度）forthesheetpiletobesafe!Seeequationsbelow:Nowaterpressureisconsidered:self-balanced（自平衡）19第19页20第20页21第21页22第22页23第23页取得压力图形步骤24第24页最大弯矩计算剪力为0点25第25页26第26页27第27页28第28页29第29页30第30页31第31页6.5CantileverSheetPilingPenetratingClayL3=D-L4TwoequationsforDandL4Fixedearthmethod(bendinghere)32第32页33第33页L3=D-L4TwoequationsforDandL434第34页35第35页36第36页37第37页38第38页39第39页40第40页41第41页Freeearthmethod(nobendingat“O”)(simpleandgood):fromSoilMechanicsbyCraig()42第42页Watertablesinfrontandbackofthesheetpileisthesame.Thereisnoseepage.Thewaterpressureisself-balanced.2.25m0.225m>0.25mDepthd=2.75m6.25m7m6.625m43第43页44第44页FromTable5.6(a)withd=2.75andhorizontalforceequilibriumWhy6.625m?45第45页Freeearthmethod:morefromDrYMChengR=?andcheckingD46第46页R=?andNOcheckingDH47第47页水头差渗流路径水力梯度48第48页R=?andNOchecking试算时，可取D=h49第49页50第50页51第51页6.6AnchoredSheetWallsFreeFixedbyearthTwomethods:Freeearthsupport(simpleandgood)Fixedearthsupport(complicatedandmoreaccurate)Dfreeearth<Dfixedearth52第52页53第53页6.7FreeEarthSupportMethodforPenetrationofSandySoil(c’=0)

Arevisedapproachcanbeusedforcohesivesoilwithc’andf’–how?54第54页55第55页56第56页57第57页

Revisedapproachcanbeusedforcohesivesoilwithc’andf’–how?58第58页Freeearthmethod:fromSoilMechanicsbyCraig()59第59页Twoequations(momentatAandhorizontalforceequilibriums)fortwounknowns(dandT)60第60页61第61页62第62页63第63页ConsideringeffectivestressincreaseduetoseepageConsideringeffectivestressdecreaseduetoseepageThisisatrialanderrormethod64第64页Seetherightfigure,forFr=2.0,dis6.3mForlimitcaseofFr=1.0,dis4.2m65第65页Thisisonsafeside.66第66页67第67页Themaximumbendingmomentandshearforcecanbefoundfordesignpurpose.68第68页Freeearthmethod:morefromDrYMChengDredgelinex69第69页Noconsiderationontheeffectivestressincrease/decreaseduetoseepage;butokasasimpleapproach70第70页71第71页6.8MomentReductionforAnchoredSheetPileWallsWhyreduction?Mmaxfromthepreviousmethod(freeearthmethod)maybereducedsincesheetpilesareflexible,leadingtoredistributionofearthpressures.Howtomakecorrectionforthereduction?Notcoveredinthissubject!

72第72页73第73页74第74页75第75页76第76页6.9FreeEarthSupportMethodforPenetrationofClay77第77页78第78页79第79页80第80页81第