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中英文对照外文翻译（文档含英文原文和汉字翻译）Deep Ex cav at ionsABSTR ACTAll majortopics in the design of in-situ retainingsystemsfor deep excavations inurban areasare outlined.Type of wall,water relatedproblemsand water pressures,lateral earth pressures,type oftechnique whereexcavationof wallis madepossible byfilling andkeeping the wall cavityfull withbentonite-watermixture duringexcavation toprevent collapseof theexcavated verticalsurfaces.Wallthickness varies between
0.50m and
1.50m.The wallis constructedpanel bypanel infull depth.Panel lengthsare2m to10m.Short lengths2-
2.5m are selected inunstable soilsor undervery highsurcharges.Nowadays depth of panelswater stopsexceeded100m,excavation depthsexceeded50m.Different panelshapes otherthan theconventional straightsection likeT,L,H,Y,+arepossiblused toform andfor specialpurposes.Panel excavationis made by cableor kellysupportedbuckets andby arecent designcalled,,cutter or〃hydrofraise whichis apairof hydraulicallyoperated rotatingdisks providedwith hardcutting tools.Excavation in rock ispossible.Slurry walltechnique is a specializedtechnique andapartfrom thebucket orthe framecarrying thecutter equipmentlike crawlercrane,pumps,tanks,desanding equipment,air lifts,screens,cyclones,silos,mixers,extractor are needed.Tremieconcrete is placed in the slurrystarting fromthe bottomafter lowreinforcementringcages.Joint between the panels is asignificant detailin waterbearing soils and steelpipe,H-beam orwater stopsare used.
1.
1.5R einforcedC oncreteR etaining WallsExcavation inStagesIt is a common type ofstaged excavationwall usuallysupported byground anchors.Soilswith some cohesion aresuitable becauseeach stageis firstexcavated bforeformwork and concreteplacement.No water table orappreciable amountof watershould be present.Sometimes micropilesupport is givenif requireddue toexpected cave-ins.
1.
1.6Soil NailWallsSimilar to the methodabove excavationis madestep bystep
1.5to2m high.Shotcreteis commonfor facingand wiremeshis used.Soft facingis alsopossible making use ofgeotextiles.Hole isdrilled,ordinary steelbars arelowered,and groutisplacedwithout anypressure.Soilshould besomewhat cohesiveand nowater tableor significantwater flowshould bepresent.
1.
1.7Coffer damsCofferdamis atemporary earth retaining structureto beable tomake excavationforconstruction activities.It isusually preferred in thecoastal andsea environmentlike bridgepiersand abutmentsin rivers,lakes etc.,wharves,quay wal1s,docks,break watersand otherstructuresfor shoreprotection,large waterfrontstructures such as pumphouses,subjected toheavyvertical andhorizontal loads.Sheet pilingis commonlyused invarious formsother thanconventionalwalls likecircular cellularbodies or double wallsconnected insideand filledwithsand.Stability ismaintained bysheeting drivendeeper thanbase,sand bodybetween sheetingandinside tierods.Earth embankmentsandconcretebodies are also used.Contiguous,tangent,secant pilesor diaphragm walls areconstructed incircular shapes,and nointernal bracingoranchoring isused toform acofferdam.Reinforced concretewaling beamssupport by arching.Shaftsare alsomade withthis method.Large excavationsor projectdetails mayrequire additionalateralsupport.
1.
1.8J etGrout andDeep Mixed WallsRetainingwalls aremadebysingle totriple rowof jetgrout columnsor deep mixed columns.There is a soilmixed wallSMW techniquespecially developedfor wallconstruction whereHsections are used forreinforcement.Single reinforcingbar isplaced in the centralhole openedfor jetgrout columns.Anchors,nailsor strutsmay be used forsupport.
1.
1.9Top DownConstr uctionRetainingstructure generallydiaphragmwallis designedand constructedas permanentload bearing wallsof basement.Piles orbarettes aresimilarly placedto completethe structuralframe.Top slabis castat theground surfacelevel,and excavationis madeunder theslab bysmallersized excavatorsand continuedownforming basementslabs ateach level.There arespecialconnection details.Top downmethod ispreferred inhighly populatedcity centerswhere horizontaland vertical displacementsare verycritical,and anchorsand strutsare verydifficult tousedue tocomplexunderground facilitiesand lifelinestructures andsite operationsare difficulttoperform.
1.
1.10Pa rtia1Excavation orIsland MethodIt ispossible togive strutsupport toretaining wallsat alater stageafter constructingcentralsections of a buildingin largesize excavations.Core thestructure isbuilt at thecentral partmaking slopedexcavations atperipheral areasand thenthe coreframe isused togivesupport towalls Figure
1.
9.It may be morepractical andconstruction timemay belesscompared toconventional bracedsystem.This methodmay notbe suitable in soft and weaksoilsdue tostablity anddeformation problemsduring slopedexcavations.
2.EA RTHPR ESSUR ESON IN-SITU RETAINING WAL L S
2.
1.IntroductionEarth pressureson in-situ retaining walls arerather differentthan thoseonordinary retaining walls due to thesupporting elments.Free displacement of walls are notallowed.Type ofsupport affectsthe distributiofn earth pressure.Strutloads weremeasured instrutted excavationsin manycountries in the past,and recommendationsweregiven.Ground anchortechnology isrelatively new,and dataoninstrumented anchored walls fortotal latepressure andfor waterpressure arebeingaccumulated.Earth pressurediagrams on strutted andanchored walls are expectedto besomewhatdifferent due to stiffersupport conditionsin theformer.Theoretical approacheswill alsobe discussed.Terzaghi and Peck1967andPeck1969based onload measurementson
2.
2.Ea rth PressureDistr ibutionson Wallsstrutsrecommend thepressure distributionshown inFigure
2.1for cohesionless soils.It isa uniformpressure andgiven byEq.
2.1；p=
0.65K Vil
2.1A twhereK is the activeearthpressurecoefficient,H is the height of wall.Unit weightY tis described as thebulk unitweight inthe originalreferences.Since bracedexcavations weregenerally dewateredinthepast projectstheunit weightintheexpression wasdescribedas wet orbulk.If waLTherectangular diagramproposed inthe figureis notan actualpressure distributionbutan envelopeobtained byplotting themeasured strut loads convertedto pressure distributionateach stageof excavationincluding thefinal depthcovering alldistributions.It isalso calledapparentpressuredistribution.It isregarded asa conservativeapproach becauseywet unitweight ofsoil,buoyant under watert二+water K=1-sin p/Hsin=tan:45-p*/2pressure6=angle of internal frictionAstrutloads calculatedby suchan envelopeare generallygreater than themeasured loads.Rectangular envelopewith p=
0.2Y tII isalso recommendedbyTwine andRoscoe1996based onmore recentfield measurements.Similarly use of submerged unitweight belowwater tableand additionof waterpressure isrecommended.Data oncohesive soilsare classifiedfor softto mediumstiff claysand stiffclay.Anchor ornail supportedwalls mayshow higherlateral displacements,and stressincreasesat theupper levelsof walls may besomewhat lesscompared to the distributionsonstruttedwalls.However,there areno documentedcomparisons.In thesolution ofanchoredwallsby finiteelement,boundary element,finite differencesoftwares orsimpler springmodels theanalyses may berepeated withoutassigning pre-tensions initiallylike incase ofnail supportedwalls and thenassign thecalculated reactionsas pretensions.There are also recommendationson selectionof thetype ofdistribution inrelation toheightof bracedwalls.Distributions basedon pressurecell recordsare recommended for allheightsbut distributionsbystrutloadmeasurements are not foundsuitable for walls higherthan15m,they may be usedforwallsof10-15m heightdepending on conditionsof theground andconstruction andrecommendedforheights less than10m.Another commoncase isan alluvialprofile whereclay,silt,sand layersdifferentmixed inproportionslie indifferent thicknesses.If adominant layeris oneof theabovepresentdistributions may be selected,otherwise theoreticalapproach likeCoulomb searthpressure expressionmay befollowed makinguseofeffective parameters,submerged unitweightsand addedwaterpressure.Effect of different surcharge loads onwallsmay be calculatedby stressdistributionsinelastic mediume.g.NAVFAC
1982.For theupper limit of veryrigid wallsthe distributionsaredoubled.W idesurchargeloadsmay alsobe convertedto equivalentheights ofsoil layer.
3.SUPPORTING ELEM ENTS
3.1Ground Anchors
3.
1.1IntroductionGround anchorisacommontype of supportingelement usedinthedesign andconstructionof in-situ retainingwalls.It isan installationthat iscapable oftransmitting anappliedtensile loadto aloadbearingstratum whichmay bea soilor rock.A summaryabout groundanchorswill begiven inthis section.Types,capacity,design,construction andquality controlwillbe reviewed.
3.
1.2Types andC apacity ofAnchor sTemporaryanchor andpermanent anchor are the main typesand asthe namesimply theformeris usedin temporaryworks andusually aperiod ofmaximum twoyears areassigned asthe designlife.Design lifeofapermanent anchoris the same asthe lifeof structure.Corrosion protectiondetailsand factorsof safetyare themain differencesbetween thetwo types.Free lengthisafunction ofheightofthewall.Fixed lengthis selectedaccording totype ofsoil and itvariesbetween3m and10m.Fixed lengthisthetensile loadbearing partof ananchor in soil.There aredifferent mechanismsof stresstransfer fromthe fixedanchor zonetosurrounding ground.support,solution toearthretainingwalls,types offailure,internal and external stabilityproblems.KEYW ORDSdeep excavation；retainingwall；earthpressure；INTR0DUCTIONNumbers ofdeep excavationpits incity centersare increasingevery year.Buildings,streetssurrounding excavationlocations anddesignofvery deepbasements makeexcavations formidableprojects.This chapterhas beenorganized insuchaway thatsubjects relatedto deep excavationprojects aresummarized inseveral sectionsintheorder ofdesign routine.These aretypes ofin-situ walls,water pressuresand waterrelated problems.Earth pressuresin cohesionless andcohesive soilsare presentedin twodifferent categories.Ground anchors,struts andnails assupporting elementsare explained.It isusually referencedas„bond stressand depends on soiltype andgrouting procedure.Excepting specialconstructions infixed partof anchorslike underreams in stiff clays,jetgrouted bodiesor inflatedaluminum bags,most commontype ofconstruction iscement andwatergrout withsome additives.Very stiff,hard soilsand romanchettecks may be groutedwithoutpressure.Many soils maybe grouted butgrouting pressure,water cement ratio w/c andadditivesplay majorrole dependingon thepermeability andstiffness ofthe soil.Fixed lengthof anchorenlargesin diameterwith increasinggrout pressure.Grout permeatesor fracturesor pushesthesoil arounddependingontype ofsoil,grout andpressure level.Coarse andfine grainedgranularsoils,alluvial soilsand weakrocks aregenerally groutedwith severalbars ofpressure throughcasingor usingpacker.Stiff cohesive soilsandfine cohesionlesssoilsmaybegroutedat higherpressuresgreater than15-20bars toform highlyfractured largerfixed endbodiesto obtainhigher capacities.Post-grouting techniquesthrough tubeand manchettesleeve tubingordouble/triple tubingare used.Mainpossibilitin esfailure ofa singleanchorarefailure ofground/grout interface,tendon itselforgrout/tendon interface.Capacity of anchors incohesionlesssoilsdepends onaverage grainsizeD50,uniformity coefficientCU,relative densityRD,diameter ofdrill hole,method ofgroutinjection primary/secondary andgrout pressure.Higher D50,CU,RD andgrout pressuresuitinhighercapacities.Fixed lengthsof4to8m arein useand6m seemsto bea lower limitof recommendation forfine tomedium sands,and thelowerlimitmaybeless forgravelly soils.Permeability andgrout characteristicsi.e.water-cementratio,pressure arekey factorsforcapacities.At lowerpressure levelslessthan1M Paand higherpressures morethan2MPa capacitiesfrom400/500to1400/1700kN areobserved infine tomedium sandsand densecoarsersands andgravels respectively.This widerange isdue toenlargement ofthe drillhole andmoregrout intrusionin coarsersoils.Calculations bysoil mechanicsprinciples cannotexplain thesecapacities.Best wayis toperform testson designanchors.Load capacityof anchors in claysis lowcompared tosandy andgravelly soils.Fixed anchorlengthsin designare usually7-8m.Application oflow groutingpressure lessthan1MPa anduseof casingtubes maybe beneficialto thecapacity.Casing tubesalso preventformation ofremoldedsoft cohesivefilm onborehole surfacein layeredsoils whichreduces capacitysignificantly.Capacity ofanchors can be increasedinstifffissured claysusing highpressuregrouting andpost-grouting.High pressurecauses hydrofracturingand/or penetrationof groutintoexisting fissures.Using bellsorunder-reams inthe fixedanchor zonein stifferclays cU90kPa alsoincrease；capacity.Tremie groutedstraight shaftsin verystiff orhard soilsyield sufficiencapacitiesi milartoanchorsinrock.Skin frictionm increaseswith decreasingplasticity andincreasingconsistency wL-w/IP mrange isfrom50to morethai400kPa instiff clays.Pressure groutingisalso usedinrock.Skin frictionor bomvalues forvariety ofrocks canbe foundin BS8081and otherreferences.Grout isin tensionlike the tendon,and itis assumedthat ultimatebond stressbetweengrout andtendon isuniform.For cleanstrandsand deformedbars alimitof2MPa isrecommended.Bond strengthcanbesignificantlyaffected bythe surfacecondition ofthetendon,particularly whenloose andlubricant materialsorloose rust,soil,paint arepresent at the interface.Minimum groutcompressive strengthof30MPa isrecommended priorto stressing.At grout/encapsulation interfacemaximum ultimatebondis taken3M Pa.Encapsulations areusually usedin permanentanchor applicationsagainstcorrosion,and singleordoubleconcentric corrugatedplastic ormetal ductscover singleormulti-unitendons andgrouted.Details athead,free length,seal betweenfree andfixed lengthsandfixed lengthvary inmany differentpatented designsSee forexample FIP,
1986.
3.
1.3Planning ofAnchor sFreelength ateach excavationstage andfixed lengthareFixed selected.length incohesionlessandcohesivesoilshas beendiscussed inthe previoussection.It isusually keptconstant in a project.Fixed lengthhas tobe placedoutside theactivewedge behindwall.It iscustomary toadd anextra tofree length.This isespeciallyuseful in projects instiff clayswhere deformationsattheback ofwall extendto distancesthreetimes thedepth of excavation.Minimum spacing ofanchorsshould be
1.5-2m andminimum distanceof2-3m shouldbe providedbetweenthefixed lengths.An anchordensity of3-8m2/anchor generallyobserved inprojectsdependsonfactors suchas waterpressure,type ofsoil,depthofexcavationetc.If closelyspaced anchors are usedeither adjacentanchorsaredesigned at different angleswiththe horizontallike10°and15°or identicalrows arenot used.Angles between5°and25°w iththe horizontalare normallyselected unlessfixed lengthsare locatedin deepercompetentlayers.Two anchorsmaybeplaced atthesameanchor headatdifferentangles ifrequired.It isconsidered agood practiceto designpositions offixed lengthsinadisorderlymanner.Another recommendationis tokeep thewhole fixed length ina singlelayer inlayeredsoils ifpossible.Distance offixedlengthto anyadjacent foundation/underground serviceisrecommended3m minimum.Spacing ofanchors iscontrolled bytype ofwall,andverticaldistancebetween rowsis determinedbyatrial anderror processi.e.anchor capacityvs.spacing,reaction forcesetc..深基坑工程摘要本文概述了城市中保留原址深基础连续墙系统对墙体，水相关问题和挡土墙方案，土锚杆类型和安装进行了阐述关键词深基坑，土压力，挡土墙，土锚杆、土锚杆安装综述伴随城市中心采取深基坑作为基础和采取深地下室设计建筑物和数量逐年增加，使得深基坑工程施工难度也显著增大本章以与在原址上深基坑工程关于次序分成几部分行文对墙体，水压力和水关于问题类型进行讨论因为土压力特征在非粘性土和粘性土之间，表现出了两种完全不一样性质所以锚固，支撑和土钉等支撑系统出现就是顺理成章了近几年来，与其余方式相比，锚固得到了广泛使用和推广挡土墙系统稳定性能够分为内部和外部稳定性对于其受到剪力、瞬间位移、支撑系统反作用力、土压力和水压力造成了其使用分析方法是与地上部分是不一样也对支撑土钉墙三种方法结果进行了比较
1.挡土墙种类
1、1介绍在实际工程应用中，许多不一样类型连续墙被用来做深基坑支护系统选取何种类型连续墙标准是，基坑尺寸、土质条件、地下水深度、各种不一样结构限制、可施工性、造价、施工速度与其余条件其中，主要考虑是墙体水密性以下是地下连续墙种类
1、支撑墙，排桩式地下连续墙
2、板桩墙，井圈护壁墙
3、桩墙
4、地下连续墙
5、阶段性基坑钢筋混凝土挡护墙
6、土钉墙
7、围堰
8、深层喷射搅拌桩
9、逆作法施工
10、局部开挖或筑岛法
1.
1.1支撑墙当进行到基槽开挖并安放排桩式地下连续墙时，于基槽周围约2到3米间隔内，采取H型、I型钢板或者采取钢丝绑扎固定并进行围挡水平或者纵向支撑系统（撑杆，锚栓，钉）也同时进行修建排桩式地下连续墙经常被广泛应用在城市一些地下存在大面积孔洞地域，采取木质排桩时，需要间隔放置在地下连续墙之间能够采取多个方法安放绑扎桩比如采取预制，原址混凝土或者是木桩进行安放依照土质情况，能够在相对浅基槽部分不采取钢筋绑扎从历史角度出发，支撑墙系统作为支持系统有久远历史在二十世纪七十年代锚固施工工艺出现之前，支撑墙系统广泛应用于各类工程，泥土混合粘性土在地下水位以上施工在施工条件允许情况下，经常采取支撑墙系统作为基槽开挖施工支撑系统支撑杆支架经惯用在施工场地狭窄管道铺设基槽开挖或者其余相类似情况，同时也用在超深超大基槽开挖情况下伴随机械化发展，土锚杆支撑系统应用也越来越多在没有梁结构约束下，能够直接采取围筒式支护结构或者锚固
1.
1.2板桩墙，井圈护壁墙板桩支架是一个薄截面（7-30毫米），400-500毫米直径钢管支撑系统能够依照不一样需要制作成U形或者Z型钢管支架由防水扣件人工连接安装因为该施工工艺受到环境原因如噪音，震动等原因在城市受到限制伴随静压工艺出现，击锤产生震动和泥土扰动相比之前工艺是最小施工最终静，压桩在土壤中组成墙体，墙体内侧经过锚固和撑杆组成支撑系统，为开挖基槽提供支撑这种工艺经常在含水量高或者软土地域应用钢管支架是最常使用，但因其灌入深度与沉降控制较困难，故有时在软土中应用预应力钢管部件较困难同时，钢板桩支架在密实土壤、塑性低土壤或者卵石土里安装困难此时可采取泥浆喷射安装，经过湿润土壤以降低安装时穿透土层难度在类似安装困难土壤中，钢管桩安装方案应该由施工方根据实际情况采取方法，而不是在设计时即确定施工方案另一个经常碰到问题是在静压钢管施工过程中钢管连接部分因为暴露在地下水部分造成连接部分漏水管桩墙经惯用于暂时目标支护结构，同时也大量应用于永久工程项目在作为暂时支护项目中，该施工方法所用部件在工程完成之后是能够回收，工程部件经过回收后，经过保养维护能够投入新工程中，不过在城市密集建筑中回收部件这一个方法是不明智，会造成其余建筑物沉降抑或者会破坏周围建筑物原本稳定结构
1.
1.3桩墙原址桩挡土墙在因为其施工造价经济性优越和可行性高，所以在工程中应用非常广泛现在桩墙有许多个类在连续（间歇）钻孔桩施工中，桩之间间距应该小于桩直径该间距应基于土壤种类和设计深度来确定，不过依照经验，间距不能很大，除了土壤种类和设计间距外，为了预防大块土壤塌落，也需要其余预防方法该施工工艺能够适适用于块土、粘结性高土壤和地下水水位以上工程，同时在一定范围内地下水工程也能够适用，但需要进行排水该施工工艺桩直径常见为
0.6米、
0.8米和
1.0米横挡系统（常见称谓为“胸撑”）混合泥浆布置在当地下连续墙不适用情况（换而言之，即地下水存在情况下）不过落后施工工艺会产生很多问题Anchors aregiven moreemphasis comparedto othersduetowidespread useobservedintherecent years.Stability ofretaining systemsare discussedas internalandexternalstability.Solution ofwalls forshears,moments,displacements andsupport reactionsunder earthandwater pressuresare obtainedmakinguseofdifferentmethods ofanalysis.A pile wallsupported byanchors issolved bythree methodsandtheresults arecompared.Type ofwallfailures,observed wallmovements andinstrumentation ofdeepexcavationprojects aresummarized.
1.TYPES OFEARTH RETAINING WALLS
1.1IntroductionMore thanseveral types ofin-situ wallsareusedto supportexcavations.The criteriaforthe selectionof type ofwallare sizeofexcavation,ground conditions,groundwater level,vertical andhorizontal displacementsof adjacentgroundand limitationsof variousstructures,availability ofconstruction,cost,钻孔桩墙用于那些空间排放小于直径SD地方它本身是一个防水结构墙相对于地下连续墙，它在在小型或者中型膨润土基槽开挖方案中造价显著降低一样，它们都需要场地来放置施工机械，能够用“硬一硬”或者“软一硬”混凝土来制成“软”混凝土桩就是一个用低强度混凝土混合粘性土制成施工时第一段桩无钢筋，切断第一段桩桩头之后接入钢筋桩桩施工方法在各国都不一样,但基本工序都需要套管支架，膨润土，连续旋翼式螺钻作为施工准备等除了钢管桩墙之外，大部分桩墙都需要混凝土作为加强或者需要用钢肋加强
1.
1.4地下连续墙地下连续墙提供了完整连续支持和防水功效地下连续墙尤其在地下水位以下大型深基坑工程如大型市政建筑，地下停车场等基础开挖经典做法因混凝土性质使制成地下结构拥有了防水和防坍塌功效，所以连续墙也称为高强度槽壁地下连续墙墙体厚度介于
0.5米到
1.0米之间由一道道连续墙体组成单个墙体长度由2米到10米不等短墙体2-
2.5米经常在不稳定土壤部分使用如今，连续墙最深深度已经达成100米，基槽开挖宽也度超出50米不一样情况和使用环境决定了墙体形状不一样，如T型、L型、H型、Y型和十字型基槽壁板经过缆绳、钻杆支撑筒体或者最新设计叫做“切割器”或者经过使用一双水力驱动“水力较刀”经过操作高强度削盘工具进行挖掘假如开挖基槽在岩石地域也是可行泥浆护壁墙技术是一个特殊区分于套筒或者其余工艺一个方法其需要履带起重机、泵、罐清砂装置、、升降机、框架切割装备、钻、搅拌机、风机等装备开始施工时，把混凝土导管放置在底部，从底部向上浇筑其中需要重点关注是饱和水土壤、钢管，H型梁
1.
1.5阶段性基坑钢筋混凝土挡护墙这是一个常见采取土锚杆固定阶段性基槽开挖支护伎俩因开挖后放入框架和混凝土而适适用于无地下水或者施工在地下水平面以上粘土地域在该地域适用时，能够采取微型桩支撑以达成期望预防井壁坍塌情况
1.
1.6土钉墙与上文阶段性基坑钢筋混凝土挡护墙施工方法相同，需要逐步进行制作（
1.5米到2米高）土钉喷网支护经惯用喷射混凝土进行表面硬化除此之外，也能够用松软土工布进行表面覆盖当孔洞做好之后，插入钢棒，覆盖上网者或土工织物，然后向其表面进行无压喷射施工进行到时，土壤出现轻微粘性或者有显著水流时即完成
1.
1.7围堰围堰是一个暂时保持土壤结构使基坑开挖顺利进行施工活动它经常使用于海岸或者海洋环境工程中，比如湖中桥墩、河堤道路、船坞、防波堤桥墩、或者其余需要进行短时间保护大型水下结构工程泵站等为了承受巨大垂直和水平荷载基础进行工程时，可使用多个方式，如内部填充沙土圆形套管或者是双层内部连接墙体深于基础排桩功效是保持稳定性，填充沙子作用是提升套筒或者是双层强题质量以预防受到流体冲击而产生位移除此之外，也应该采取土堤和混凝土块进行稳定在套管内部，连续、相互垂直桩或者是地下连续墙或者是无内部支撑系统也能够应用在围堰施工方案中钢筋混凝土横梁由弯曲壁板进行支撑假如是巨型基槽结构，施工时必须需要其额外支撑系统进行支撑
1.
1.8深层喷射搅拌桩该施工工艺做成挡土墙是用单排或者是三排旋喷柱或者是深层搅拌柱组成这个称谓泥浆混合墙SMW技术，这个技术源自于H型结构所应用地下连续墙加固方法单根增强钢筋放置于喷射搅拌柱孔洞中心能够用土锚杆、土钉撑杆作为支撑
1.
1.9逆作法施工挡土墙通常是地下连续墙作为永久基础承载作用设计和施工桩基和墙基础共同组成结构框架先浇筑顶板于设计地坪标高处，然后使用小型挖掘机对基槽进行开挖，然后继续对各层进行搭建顶板继续开挖一一这是一个特殊施工方式逆作法施工通常优先应用于建筑密集，因为地下设备设置太多而无法使用土锚杆、锚固和撑杆系统城市中心
1.
1.10局部开挖或筑岛法这个施工方法能够为后期建设中心部分大型基槽挡土墙结构以支撑这个施工方法关键是在基槽边缘地域建造带有斜坡挡护，然后中心部分剩下土壤以用来支撑连续墙这个施工方法可能会更实际而且花费时间会少于使用常规基础支撑方法项目不过因为土层稳定性和变形等问题，这个方法不适用与软土和软弱土层
2.原位挡土墙土压力
2.1综述因为支撑系统不一样，原位挡土墙土压力与日常挡土墙是不一样自由替换挡土墙在这里是不允许，支撑种类不一样，会造成土压力不一样过去在许多国家，受撑基坑支撑产生荷载曾经被测算，而且给出了推荐数值土锚杆施工方法是最近出现，锚固式墙体所受到土压力和水压力已经被仪器测算出因为支撑方式不一样，撑杆式支撑和锚固式支撑在土压力测算数据中显示出了不一样而就理论也将会被重新考虑
2.2连续墙土压力分布基于Te rzaghi和Peck荷载测量，得出了土压力分布推荐数值公式p=
0.65K VHAt其中，KA是活跃土压力系数，H是挡土墙高Y是把泥土看作整块土壤，t鉴于基槽过去经常被认为是干燥，数据能够参考规范中数值假如墙体在充满地下水处，且是不透水，则浮力必须加入计算V二泥土在水下浮力K=1s inB/1+sin3=tan245-3/2一B二内摩擦角度依照公式计算出来数据并不能十分准确计算出土压力分布，不过能够根据数据测量出相对靠近计算出各个部分土压力分布荷载，也能够称作可测算士压力分布同时，基于近期研究结果，Twi ne和Ros coe也推荐计算时采用P=
0.2Y H这一公式，它得出结论与上一公式在水中或者加水之后压力是t相同在松软土和中硬度土、黏土、硬黏土土壤计算中，粘性土相关资料也是能够直接采取相比于支撑系统，锚固和土钉墙支撑系统受到更多侧向压力即使如此但，是还未有明确数据来证实这个推论在锚固计算处理方法中，不一样软件或者模型都采取了有限元计算，边界计算等方法进行分析，像计算土钉支撑系统方法一样，首先进行应力计算，随即在结构中应力，随即把计算出来应力分配到锚固系统当中，作为先应力计算结果当然也有与支撑墙高度分布类型关系选择提议压力分布数据统计基于对土壤颗粒压力统计，但对全部负荷测量统计都显示，这种施工方法不适合15米以上连续墙建造从地面和施工条件出发，它只可用于墙面10-15米高度，提议地下墙深度不超出10米工地使用常见其余案例是在由不同成份、不一样厚度混合黏土、淤泥、沙粒堆积成淤积层上使用假如某个比较厚土层中某个性质土壤占据主要性质，能够采取该土层作为参数进行应力分配计算，不然采取“库伦”理论和其研究出土压力表示式，需要单位重量和淹没部分和增加水重量作为参数进行计算在不一样额外荷载作用下，因刚性墙体承载上限是分配到荷载2倍，墙体受到影响能够经过弹性介质进进行分配在纵向附加荷载下，其受力传导至竖向墙体，随即传导至土层
3.支撑系统
3.1土锚杆
3.
1.1介绍土锚杆是一个常见用于原址墙设计和施工支撑，是一个能够把力传导土沙或岩石持力层上一个装置本部分内容对土锚杆类型，功效，设计、施工和质量控制进行回顾
3.
1.2土锚杆类型和功效土锚杆能够分成暂时或者永久土锚杆，正如同从称呼上来说，暂时土锚杆最大设计寿命是2年，而永久埋设土锚杆，其设计寿命与建筑物结构设计寿命是等长出了设计年限区分，二者最大区分还在于对受腐蚀部位保护和对安全原因考虑由槽壁高度确定土锚杆自由端长度是土锚杆一个特点，而土锚杆抗张力部分是埋置在土壤中，所以需要依照3米到10米深范围内种土壤类来选择土锚杆固定长度现在有不一样装置能够使压力从固定杆传导至周围土壤中这种取决于士培情况和施工进度而产生力被称为“粘结土压力”除在硬黏土特殊土壤条件下采取旋喷桩或膨胀铝袋等外，都采取了水泥混合其余外加剂作为土锚杆制作材料，在超硬土或者岩石地域，则采取是无压灌浆法进行施工土壤间空隙会被灌入泥浆填满，土壤渗透性和硬度决定了水灰比和外加剂种类固定长度土锚杆伴随泥浆压力加大而造成直径变大土壤条件、泥浆类型和压力大小决定了泥浆渗透速率、对土壤挤压程度在粗、细颗粒土壤，河流淤积土和软弱岩层施工灌浆时，经惯用几根钢筋集束或者对钢筋进行包装后放入塑性低土和性状良好非粘性土中，为了填充可能形成断裂带，需要更大压力使末端有足够空间进行填充后灌浆技术是用单个或者双管进行浇注这个施工技术主要风险在于泥浆连接面、预应力钢筋本身土颗粒粒径均衡系数，相对密度，钻孔直径，注入泥浆方法，和注入压力决定了土锚杆在非粘性土壤中深度更高土颗粒均衡系数，相对密度，成孔直径和灌浆压力会加大钻孔直径现在使用是长度4米到8米固定长度锚，在土质良好土壤里，6米为下限长度，在沙砾土中能够比6米更低渗透性和泥浆参数（比如水灰比，压力）是成孔关键，中性土或粗砂在低压（小于1兆帕）和高压（大于2兆帕）时，成孔压力从400KN到1700千牛效果是很显著这个宽大范围是因为扩大孔洞和灌入泥浆造成不过理论上计算无法解释这个孔洞容量原位测试是提供设计依据最好方法土锚杆荷载能力在粘土中比沙土和沙砾中更低粘土中土锚杆固定杆长度经常设计为7到8米使用低压小于1兆帕和套管对成孔是有益套管也能够预防形成重塑软土和在孔中形成结合膜使用高压轻易造成后浇法施工地下孔开裂，高压会引发水力压裂在塑性低使用喇叭形桩也会增加孔洞容积在超硬土地域或者是硬砂地域使用混凝土导管关注泥浆，其效果于岩层锚杆相同在低塑性土中，摩擦力伴随粘性降低和浓度增加而从50千帕增加到400千帕以上一样，压力灌浆也用在岩石地域表面摩擦力或者各种石头之间参数能够在BS8081规范中得到参考值在预应力钢筋部分灌浆，假设钢筋和灌浆之间均匀结合推荐在清理之钢筋预应力限制在2兆帕之内钢筋表面情况会影响成型之后结构强度，尤其是在光滑表面、涂上润滑剂之后或者除锈、土壤情况下在以前经常采取抗压强度为30兆帕以上泥浆作为材料，以3兆帕压力作为最大钢筋连接强度而集束钢筋经惯用在永久性质土锚杆中用以预防腐蚀，并用单双层塑料管或是金属套件进行包装杆头，自由端长度等数据，能够参考FIP,1986o
3.
1.3土锚杆安装在基槽建设各个阶段，锚杆自由端和固定杆都必不可少因在施工过程中锚杆是不能移动，故在粘结力差土壤和在粘结土中固定杆需要在工程施工之前提前做好习惯上将锚杆固定杆与在槽壁后活动楔形装置连接，作为固定系统一部分这个楔形装置经惯用在槽壁后大于3倍槽深被破坏且塑性低土壤中，楔形固定装置最小距离要求是
1.5米到2米，而固定杆最小距离应为2到3米依照水压、土壤种类不一样，依照实际情况采取每3平方米一一8平方米一根土锚杆规律布置假如小间距使用锚杆，每个锚杆水平角度必须相差10°或者15，或者不整排布置在通常施工中，除非固定杆埋设在足够深土层中，不然经常采取水平错开5°到25°方法假如必须在一个杆头安装两杆，则水平角度必须错开在实践中，错开放置固定杆或者固定杆无规律安装取得了良好效果另一个推荐方法是假如可能情况下，统一土锚杆固定杆在同一层土层中，这时，固定杆长度应连续墙种类，应该保持在3米以上，水平间距也应由其确定每排土锚杆间距应该由实际情况确定（比如土锚容量相对于间距，应力等）speed ofwork andothers.One ofthemaindecisions isthe water-tightness ofwall.The followingtypesofin-situ wallswill besummarized below；
1.Braced walls,soldier pileand laggingwalls
2.Sheet-piling orsheet pilewalls
3.Pile wallscontiguous,secant
4.Diaphragm wallsor slurrytrench walls
5.Reinforced concretecast—in—situ orprefabricated retainingwalls
6.Soil nailwalls
7.Cofferdams
8.Jet-grout anddeepmixedwalls
9.Top-down construction
10.Partial excavationor islandmethod
1.
1.1Br acedWallsExcavation proceedsstep bystep afterplacementofsoldier pilesor socalled kingpostsaround theexcavation atabout2to3m intervals.These maybe steelH,I orWF sections.Rail sectionsand timberarealso used.At eachlevel horizontalwaling beamsand supportingelementsstruts,anchors,nails areconstructed.Soldier piles are drivenor commonlyplacedin boredholes inurban areas,and timberlagging isplaced betweensoldier pilesduring theexcavation.Various detailsof placementof laggingare available,however,precast units,in-situ concreteor shotcretemay alsobeusedas alternativeto timber.Depending ongroundconditions nolagging maybe providedin relativelyshallow pits.Historically bracedwallsarestrut supported.They hadbeen usedextensively beforetheground anchortechnology wasdeveloped in1970s.Soils withsomecohesionand withoutwatertable areusually suitablefor thistype ofconstruction ordewatering isaccompanied ifrequiredand allowed.Strut support is commonlypreferredinnarrow excavationsfor pipelaying orsimilar worksbutalso usedin deepand largeexcavations SeeFig
1.
1.Ground anchorsupportisincreasinglyused andpreferredue toaccess forconstruction worksand machinery.Waling beamsmaybeusedor anchorsmaybeplaced directlyon soldierpiles withoutany beams.
1.
1.2Sheet-piling orSheet PileWallsSheet pile isa thinsteel section7-30mm thick400-500mm wide.It ismanufactured indifferentlengths andshapes likeU,Z andstraight linesections Fig.
1.
2.There areinterlockingwatertight groovesatthesides,an theyare driveninto soilby hammeringorvibrating.Their useis oftenrestricted inurbanized areasduetoenvironmental problemslikenoise andvibrations.New generationhammers generateminimum vibrationand disturbance,andstatic pushingof sectionshave beenrecently possible.In softground severalsections maybedriven usinga template.Theproduct endisa watertight steelwall insoil.One sideinnerof wallis excavatedstep bystep andsupportisgiven bystruts oranchor.Walingbeams walersare frequentlyused.They areusually constructedin waterbearing soils.Steel sheet pilesarethe mostcommon butsometimes reinforcedconcrete precastsheet pilesectionsare preferredin softsoils ifdriving difficultiesarenotexpected.Steel pilesmayalso encounterdriving difficultiesin verydense,stiff soilsorinsoils withboulders.Jettingmay beaccompanied duringthe processto easepenetration.Stepile sectionslsheet usedin suchdifficultdriving conditionsareselectedaccording tothe drivingresistance ratherthan thedesign moments inthe project.Another frequentlyfaced problemistheflaws ininterlockingduring drivingwhich resultin leakagesunderwatertable.Sheetpilewallsarecommonly usedfortemporary purposesbut permanentcases arealso abundant.In temporaryworks sectionsareextracted aftertheir serviceis over,and theyare reusedafter maintenance.This processmaynot besuitableindense urbanenvironment.In-situ pileretainingwallsare verypopular dueto theiravailability andpracticability.There aredifferent typesof pilewalls Fig.
1.
3.In contiguousintermittent boredpileconstruction,spacing betweenthe pilesis greatthanthediameter ofpiles.Spacing isdecidedbased ontypeofsoilandlevel ofdesignmomentsbut itshould notbe toolarge,otherwise piecesoflumps etc.drop andextra precautionsareneeded.Cohesive soilsor soilshaving somecohesionare suitable.No watertable shouldbepresent.Acceptable amountof wateris collectedat thebaseand pumpedout.Common diametersare
0.60,
0.80,
1.00m.W alingbeams usuallycalled〃breasting beamsare Tangentpiles withgrouting inbetween areused whensecant pilingordiaphragm wallingequipment isnot availablei.e.in caseswhere groundwater exists.Poorworkmanship createssignificant problems.Secant boredpilewallsare formedby keepingspacingofpiles lessthan diameterSD.It isawatertightwall andmaybemore economicalcostof siteoperations andbentonite plant.There isalso needfor placefor theplant.It maybe constructedcomparedto diaphragmwall insmall tomedium scaleexcavations dueto“hardhard”aswe11as soft—hard”.“S oft”concrete pilecontainslow cementcontent andsome bentonite.Primary unreinforcedpiles areconstructedfirst andthen reinforcedsecondary pilesare formedby cuttingthe primarypiles.Pile constructionmethods mayvary indifferent countriesfor alltypeofpilewalls likefull casingsupport,bentonitemostly reinforcedconcrete butsheetpilesections orsteel beamsarealsoused.support,continuous flightauger CFAetc.
1.
1.4Diaphr agmWallsDiaphragm wallprovides structuralsupport andwater tightness.It isa classicaltechniquefor manydeepexcavationprojects,large civilengineering works,undergroundcar parks,metro pitsetc.especially underwatertable.These reinforcedconcrete diaphragmcontinuous wallsarealsocalled slurrytrenchwalls duetothereference giventotheconstruction。
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