《专业英语翻译》-PartⅣBridge and Tunnel

Unit4—1BridgeEngineeringTheareasofbridgeengineeringincludeplanning，analysisanddesignconstruction，maintenance，andrehabilitation.Bridgesaregreatsymbolsofmankind'sconquestofspace.Beforethe18thcentury，bridgesweremademostlyofnaturalmaterials，forinstance，wood，stone，bricks，etc.下一页返回Unit4—1BridgeEngineeringZhaoZhouBridgeinHebeiProvince

China，withmainspanof37meters，hasahistoryofmorethan1,300yearsandisstillinserviceatpresent(showninFig.1).Itisoneofthemostancientstonearchbridgesintheworld.Inthe6thcentury，ironchainsbegantobeUsedinthefootbridgesinChina.ThistechnologywasimportedintoEuropeinthe18thcentury.上一页下一页返回Unit4—1BridgeEngineeringIn1779，thefirstcast-ironarchbridge—CoalbrookdaleBridgewithaspanof30.65meterswasconstructedinBritain.Fromthemiddleofthe19thcentury，theadventofsteelfollowedbyhighstrengthsteelwiresenabledbuildingoflongspansteelbridgesandsuspensionbridgesinthewesterncountries.In1850，BritanniaBridgewitha141mlongmainsparwasbuiltinBritain.上一页下一页返回Unit4—1BridgeEngineeringItwasthefirstrailwaybridgedesignedasboxgirder.In1883，anurbansuspensionbridge，Brooklynbridge，witha486mlongmainspanwasbuiltinNewYork，America.In1890，arailwaycantilevertrussbridge，FirthofForthBridgeappearedinScotland.Itsmainspanreachedto520meters.上一页下一页返回Unit4—1BridgeEngineeringTechnicalInnovationintheFirstHalfofthe20thCenturyIn1867，theFrenchinventedtheconceptofreinforcedconcrete，whichwasfirstlyappliedtobuildingstructuresandthentobridgeconstructionm1905.Fromthenon，reinforcedconcretebridgesbecamethemainstreamofshortandmediumspanbridgestoreplacesteelbridges.Inthefirsthalfofthe20thcentury，manylongspansuspensionbridgesandarchbridgeswereconstructed.In1931，theGeorgeWashingtonBridgewasbuiltinNewYork,withamainspanreaching1,067m.(fig.2)上一页下一页返回Unit4—1BridgeEngineering1937，theGoldenGateBridgeinSanFranciscowithamainspanof1,280mwasbuilt.ThemainspanoftheBayonnesteelarchBridgebuiltin1931reachedto503.6meters.In1932，theSydneyHarborBridgewitha503metermainspanwasbuiltinAustralia.Inthe1930's，structuralanalysisanddesigntheoriesformanytypesofbridgesweresetupsuccessivelywiththedevelopmentofthebridgetechnology.Herearesomefamoustheories:上一页下一页返回Unit4—1BridgeEngineering(1)Designtheoryofreinforcedconcrete;(2)Deflectiontheoryforsuspensionbridgesandspaceanalytictheoryforsteelgirderframes;(3)Stabilityandthevibrationtheoryofstructuresandthinwallbartheory;(4)Specialanalysisandnon-lineartheoryof(5)Analytictheoryforgrillageandanalyticstructurestheoryforboxgirders;(6)Practicaldeflectiontheoryforsuspensionbridge.上一页下一页返回Unit4—1BridgeEngineeringTechnicalInnovationinthe1950'sWorldWarIIinhibitedbridgedevelopment.TheconceptofprestressedconcretewascreatedbyGugeneFreyssinetofFrancein1928，butfailedtobeappliedinpracticebecauseoftheWar.Neitherdidtheconceptofmoderncable—stayedbridgeswhichwasproposedbyFranzDischingerofGermanyin1938.Afterthe1950's，thesetwotechnologiesfoundwideapplicationwhendamagedEuropeanbridgeswererehabilitatedandrebuilt.上一页下一页返回Unit4—1BridgeEngineeringIn1950's，prestressingtechnologyandtherenaissanceofcable-stayedbridgeswerethetwogreatestachievementsinbridgedevelopment.BridgetechnologyinFranceandGermanydevelopedrapidlyinthisperiod.TechnicalInnovationinthe1960'sSevernBridgeinUKwitha988mlongmainspanbuiltin1966.Usingflatboxgirdersratherthansteeltrussgirdersandconcretepylonsthansteelpylons.上一页下一页返回Unit4—1BridgeEngineeringTechnicalInnovationinthe1970'sDuringthe1970's，prestressingtechnologybecamematureThecombinationofprestressingtechnologywithcable—stayedbridgesstartedanepochinbridgedevelopmentandtheconceptofcable-stayedbridgesspreadfromGermanytootherpartsofEurope，AmericaandJapan.上一页下一页返回Unit4—1BridgeEngineeringTechnicalInnovationinthe1980'sDuringthe1980s，Japandevelopedtheconstructionmethodformaincableswithprefabricatedparallel-wirestands(PPWSMethod)forsuspensionbridges.Thisreplacedinmostinstancesthetraditional“aerialspinningmethod”(ASMethod)firmAmerica.TechnicalInnovationinthe1990'sThe1990'swasaperiodinwhichmanybridgerecordswerebroken.上一页下一页返回Unit4—1BridgeEngineeringTheNormandiecable—stayedBridgeinFrancecompletedin1995hasamainspanof856mnoticeableforparallelstrandcablesandconstructioncontroltechnology.TheGreatBeltsuspensionBridgeinDenmarkcompletedin1997hasamainspanof1,624m，noticeableforthecollision-resistancetechnologyofpylonsandpiers.WanxianArchBridgeovertheYangtzeRiverinChinacompletedin1997hasamainspanof420m，noticeablefortheconstructioncontroltechnologyoftheconcretefilledsteelarchandcantileverconstruction.(showninFig.3)上一页下一页返回Unit4—1BridgeEngineeringTheAkashiKaikyosuspensionbridgeinJapancompletedin1998hasamainspanof1,991m，whichwasnoticeableforthedeepwaterfoundationsandtheusageofthe1,800MPahighstrengthsteelwiresforpiers，earthquakeresistancedesignofpylonsandvibration-reductiontechnology.InNorway，theStolmasundetcontinuousrigidframebridgewithamainspanof301mwascompleted1998(fig.4).Itisthelongestspanofthistypeofbridgesintheworld.上一页下一页返回Unit4—1BridgeEngineeringTheOresundStraitLinkconnectingDenmarkandSwedenisacombinedhighwayandrailwaybridge.The108mapproachspanswereconstructedbyfullspanerectionmethodwitha9,000thugefloatingcrane.Withthedevelopmentofcomputertechnology，theanalysisofbridgestructurestendstogetnumericalsolutionsmoreprecisely.Theinnovationincludes:上一页下一页返回Unit4—1BridgeEngineering(1)TheapplicationofITtechnologytotheplanning，designstructuralanalysis,constructionmanagement,healthmonitoringandmaintenancemanagement，etc.(2)Theelastic/plasticstabilityanalysisconsideringthewholeloadingstageuptotheultimatestage(3)Thethreedimensionalspatialanalysisofthewholesectionandcomplicatedparts;(4)Thenumericalimitationofcollapseprocessunderstrongearthquake;上一页下一页返回Unit4—1BridgeEngineering(5)Thenon-linearcoincidenceanalysisofthewind-inducedvibration.BridgeDevelopmentinthe21stCenturythebridgedevelopmentisshownin:(1)Planninganddesign:fastoptimizationandnumericalimitationinordertorealisticallydemonstratethefunction，safetyandlandscapeofbridgeformakingdecisions.上一页下一页返回Unit4—1BridgeEngineering(2)Manufactureanderection:GPSpositioning;remotecontrolofconstructionandmanagement;intelligentmanufacturingsystemstoproducecomponents;integralerectionbyhugeconstructionrobots.(3)Monitoringandmanagement:automaticdamagediagnosis;remoteautomaticcontrol.上一页下一页返回NewWordsandExpressionsrehabilitation n.复权，复职，复位;恢复名誉，平反，import n.进口货;进口，输入;含义;重要性cantilever vt.输入，引入，进口;表示，successively adv.接连地，相继地;依次地deflection n.[美](=deflexion)偏转，偏抖;挠曲;vibration n.震(颤、振)动;摆动;振荡;non-linear adj.非直线的;非线性的grillage 格架，板架;井格结构inhibit vt.禁止，抑制rehabilitate vt.恢复原状，修复，使康复;恢复上一页下一页返回NewWordsandExpressionspylon n.桥塔，塔状物，吊架，电缆铁塔，塔架innovation n.改革，创新spatial

adj.空间的，立体的，三维的;占大篇幅的collapse n.崩溃，倒塌，虚脱diagnosis n.审察，查究，分析，判断reinforcedconcrete钢筋混凝土floatingcrane水上浮式起重机，浮吊上一页下一页返回ExercisesI.WriteTinfrontofastatementifitistrueandwriteFifitisfalseaccordingtothetext.1.Highwaysaregreatsymbolsofmankind'sconquestofspace.2.Thefirstcast-ironarchbridgeBrooklynBridgewasconstructedinamerica.in1779.3.TheconceptofreinforcedconcretewasinventedbyGerman,whichwasfirstlyappliedtobuildingstructuresandthentobridgeconstructionin1905.上一页下一页返回Exercises4.Designtheoryofreinforcedconcreteweresetupinthe1930's.5.Theconceptofprestressedconcretewascreatedin1928，butfailedtobeappliedinpracticebecauseoftheFirstWorldWar.6.TheAkashiKaikyosuspensionBridgeinJapancompletedin1998hasamainspanof

1,991m，whichisthelongestsuspensionbridgeuptonow.上一页下一页返回Exercises7.TheStolmasundetcontinuousrigidframebridgeisacombinedhighwayandrailwaybridge.8.GPSpositioningisthegreatdevelopmentforbridgeinthe21stcentury.II.TranslatethefollowingsentencesintoChinese.1.Theareasofbridgeengineeringincludeplanning，analysisanddesign，constructionmaintenance.andrehabilitation.上一页下一页返回Exercises2.In1950's，prestressingtechnologyandtherenaissanceofcable-stayedbridgeswerethetwogreatestachievementsinbridgedevelopment.3.Withthedevelopmentofcomputertechnology，theanalysisofbridgestructurestendstogetnumericalsolutionsmoreprecisely.4.Inbridgefield，thetechnologyofautomaticdamagediagnosisandremoteautomaticcontrolwillbethegreatprogressforbridgedevelopmentinthe21stcentury.上一页下一页返回ExercisesIII.TranslatethefollowingexpressionsorsentencesintoEnglish.1.天然材料2.悬索桥3.结构分析4.钢筋混凝土5.薄壁理论6.箱梁7.浮吊8.远程施工控制和管理9.桥梁是人类征服空间距离的伟大标志。10.预应力技术和斜拉桥的复兴是桥梁发展过程的两项最伟大的成就上一页返回Unit4—2Cable—stayedBridgeCable-stayedbridges

withaself-anchoredstructure，ownmanytechnologicaladvantages

suchasreasonableperformanceofloadbearing，material—saving，highcapacityinspanning，goodadaptation，safetyandconvenienceinconstructionandsoon.Cable—stayedbridgesareconstructedalongastructuralsystemwhichcomprisedanorthotropicdeckandcontinuousgirderswhicharesupportedbystaysi.e.inclinedcablespassingoverorattachedtotowerslocatedatthemainpiers.下一页返回Unit4—2Cable—stayedBridgeWiththerisingofconstructionofurbantransportation，highwaynetsandfreewaysystemsinChinawhichhasavastterritoryandmanyinterweavingriverscable-stayedbridgespresentformidablevitalitiesUptotheendoflastcentury，thenumberofvarioustypesoflong-spancable—stayedbridgeswasabout50to60.Thelengthofamainspanincreasedfrom200mto600minthelastdecade.上一页下一页返回Unit4—2Cable—stayedBridgeTherearebasicallythreetypesoftowersinthiskindofbridges，thatis，singletowerdoubletowersandtripletowers.Inaddition，therearethreekindsofthecableplanearrangement，paralleldoublecableplanes，spatialdoublecableplanesandsinglecentralcableplane.ThebridgegirdersaremainlyprestressedconcretestructureswhosecrosssectionsaresimpleIItypesidegirdersandcomplexseparatedsideboxgirders.上一页下一页返回Unit4—2Cable—stayedBridgeWiththedevelopmentinmanufacturingtechnologyofsteelstructures，manynewtypesofdeckstructureshavebeendeveloped，forexample，compositedeckscomposedofI—shapedsteelgirdersandprefabricatedreinforcedconcreteslabs，hybriddeckslongitudinallyconnectedwithsteelboxgirdersandprestressedconcreteboxgirdersandsingledecksofsteelboxgirders.上一页下一页返回Unit4—2Cable—stayedBridgeRCtowersarecommonlyadoptedincable-stavedbridesinthemainlandofChina，whosetypesweremostlyH-shapedintheearlierstageandhavegraduallybecometheshapesofdiamondandlozenge.ThestaycablesarebasicallymadeupofgalvanizedparallelwiresprotectedwithHDPEoutside.Recentlyanewcablesystemofparallelstandswithfour-layerprotectiontechniquesisoccasionallyusedinseveralcable—stayedbridges.

上一页下一页返回Unit4—2Cable—stayedBridgeIn1991NanpuBridgeoverHuangpuRiverinShanghaiwasbuiltwithamainspanbeyond400masthefirstcable—stayedbridgeusingacompositedeckwithsteelgirderscoveredbyprecastPCslabsinChina,(showninFig.1)anditscablesprefabricatedinfactorieswereparallelwireswithHDPEprotection上一页下一页返回Unit4—2Cable—stayedBridgeSubsequently,YangpuBridgeinShanghaiwithamainspanof602mandQingzhouBridgeoverMinjiangRiverinFuzhouwithamainspanof605mareinthesametypeofbridgegirders，butthelatteradoptstheparallelstrandcablesystem.Besidesobtainingnewforeignexperiencesinbridgeconstructionsomeimprovementsindetailtreatmentsandtechnicalprocesseshavebeenmadeinthedeckstructuresofthesebridgesmentionedabove.上一页下一页返回Unit4—2Cable—stayedBridgeThemulti-spancable-stayedbridgeshavebecomearisingtendencytodayintherecentconstructionofcable—stayedbridges.InTingKauBridgeinHongKongwiththreetowersacoupleofindependentcableswereusedtokeepthebalanceofthecentraltower.DongtingLakeBridgeinHunanProvincewasbuiltin2000asathree-towercable—stayedbridgeinwhichthefullfloatingsysteminlongitudinaldirectionwasused.InYilinBridgeinYichang，HubeiProvince，athree-towercable-stayedbridge，aconsolidationsystemoftower-girder-pierwasadoptedforobtaininggoonstructurestiffness.上一页下一页返回Unit4—2Cable—stayedBridgeWuhuBridgeoverYangtzeRiverfinishedin2002(showninFig.2),isadouble—deckbridgewithtwinrailwaysbelowandfour-lanehighwaysabove.Themaingirderisasteeltrussstructureandthetowerhasonlyaheightof32mbecauseoftherestraintoflocalaviationclearance.ThisbridgehasamuchlargerscalethanHongshuiheBridgebuiltin1980withsinglerailroadandamainspanof96m.Theadvancedtechniquehasprovidedagoodexampleforthedevelopmentoflong-spanrailwaycable-stayedbridge.上一页下一页返回Unit4—2Cable—stayedBridgeManyexistingcable—stayedbridgesaremasterpiecesofsteelconstruction.Theyarepleasinginoutline，cleanintheiranatomicalconceptionandtotallyfreeofmeaninglessornamentation.Thisisbecausethedesignofcables—stayedbridgeswasgovernednotonlybyfinancial，practicalandtechnicalrequirements，butalso，toagreatextent，byaestheticalandarchitecturalconsiderations.Inthedesignofmoderncable-stayedbridges，oneobjectiveistoproduceanaestheticallyappealingbridgewhichblendswithitssurroundings.上一页下一页返回NewWordsandExpressionsanchor n.锚self-anchored adj.自锚(式)的territory n.领土，领地，版图，地区，活动范围vitality n.活力，生命力，生机prestressed adj.预应力的(混凝土)hybrid n.混血儿，杂种，混合物longitudinal adj.经度的，经线的，纵的lozenge n.菱形，菱形花纹，菱形窗玻璃aviation n.航空，航空学，飞行术上一页下一页返回NewWordsandExpressionsaesthetical adj.美学的，审美的，有审美感的surrounding n.[pl.]周围的事物，环境aviationclearance航空净空上一页返回Unit4—3BearingsBearingsarestructuraldevicespositionedbetweenthebridgesuperstructureandthesubstructure.Theirprincipalfunctionsareasfollows: 1.Totransmitloadsfromthesuperstructuretothesubstructure2.Toaccommodaterelativemovementsbetweenthesuperstructureandthesubstructure.Theforcesappliedtoabridgebearingmainlyincludesuperstructureself-weight，trafficloads，windloads，andearthquakeloads.下一页返回Unit4—3BearingsBearingsmaybeclassifiedasfixedbearingsandexpansionbearings.Fixedbearingsallowrotationsbutrestricttranslationalmovements.Expansionbearingsallowbothrotationalandtranslationalmovements.Therearenumeroustypesofbearingsavailable.Thefollowingaretheprincipaltypesofbearingscurrentlyinuse.上一页下一页返回Unit4—3BearingsSlidingBearingsAslidingbearingutilizesoneplanemetalplateslidingagainstanothertoaccommodatetranslations.Theslidingbearingsurfaceproducesafrictionalforcethatisappliedtothesuperstructure，thesubstructure，andthebearingitself.Toreducethisfrictionforce，PTFE(polytetrafluoroethylene)isoftenusedasaslidinglubricatingmaterial.InitscommonapplicationonesteelplatecoatedwithPTFEslidesagainstanotherplate，whichisusuallyofstainlesssteel.上一页下一页返回Unit4—3BearingsSlidingbearingscanbeusedaloneormoreoftenusedasacomponentinothertypesofbearings.Pureslidingbearingscanonlybeusedwhentherotationscausedbythedeflectionatthesupportsarenegligible.Aguidingsystemmaybeaddedtoaslidingbearingtocontrolthedirectionofthemovement.Itmayalsobefixedbypassinganchorboltsthroughtheplates.上一页下一页返回Unit4—3BearingsRockerandPinBearingsArockerbearingisatypeofexpansionbearingthatcomesinagreatvariety.Ittypicallyconsistsofapinatthetopthatfacilitatesrotationsandacurvedsurfaceatthebottomthataccommodatesthetranslationalmovements.(fig.1a)Apinbearingisatypeoffixedbearingsthataccommodatesrotationsthroughtheuseofasteelpin.Thetypicalconfigurationofthebearingisvirtuallythesameastherockerdescribedaboveexceptthatthebottomcurvedrockerplateisnowflatanddirectlyanchoredtotheconcretepier.(fig.1b)上一页下一页返回Unit4—3BearingsRockerandpinbearingsareprimarilyusedinsteelbridges.Theyareonlysuitablefortheapplicationswherethedirectionofthedisplacementiswelldefinedsincetheycanonlyaccommodatetranslationsand/orrotationsinonedirection.RollerBearingsRollerbearingsarecomposedofoneormorerollersbetweentwoparallelsteelplates.Singlerollerbearingscanfacilitatebothrotationsandtranslationsinthelongitudinaldirection，whileagroupofrollerswouldonlyaccommodatelongitudinaltranslations.上一页下一页返回Unit4—3BearingsInthelattercasetherotationsareprovidedbycombiningrollerswithapinbearing.Rollerbearingshavebeenusedinbothsteelandconcretebridges.ElastomericBearingsAnelastomericbearingismadeofelastomer(eithernaturalorsyntheticrubber).Itaccommodatesbothtranslationalandrotationalmovementsthroughthedeformationoftheelastomer.(fig2)上一页下一页返回NewWordsandExpressionsPTFE(polytetrafluoroethylene）聚四氟乙烯deflectionn.挠度viscous adj.粘性的，粘滞的，胶粘的bridgesuperstructure桥梁上部结构bridgebearing桥梁支座superstructureself-weight结构自重trafficload交通荷载fixedbearing固定支座expansionbearing可动支座translationalmovement直线位移slidingbearing滑动支座上一页下一页返回NewWordsandExpressionsanchorbolt锚检guidingsystem制导系统rockerbearing摇轴支座pinbearing铰支座rollerbearing滚轴支座inthelattercase后者volumetricchange体积变化bearingpad承重垫片cottonduck棉粗布，棉帆布上一页下一页返回NewWordsandExpressionspotbearing盆式支座sphericalbearing球形支座diskbearing板式支座polyetherurethane聚醚氨酯上一页返回Unit4—4PiersandColumnsPiersprovideverticalsupportsforspansatintermediatepointsandperformtwomainfunctions:transferringsuperstructureverticalloadstothefoundationsandresistinghorizontalforcesactingonthebridge.Althoughpiersaretraditionallydesignedtoresistverticalloads，itisbecomingmoreandmorecommontodesignpierstoresisthighlateralloadscausedbyseismicevents.下一页返回Unit4—4PiersandColumnsEveninsomelowseismicareas，designersarepayingmoreattentiontotheductilityaspectofthedesign.Piersarepredominantlyconstructedusingreinforcedconcrete.Steel，toalesserdegree，isalsousedforpiers.Steeltubesfilledwithconcrete(composite)columnshavegainedmoreattentionrecently.上一页下一页返回Unit4—4PiersandColumnsStructuralTypesPierisusuallyusedasageneraltermforanytypeofsubstructurelocatedbetweenhorizontalspansandfoundations.However,fromtimetotime，itisalsousedparticularlyforasolidwallinordertodistinguishitfromcolumnsorbents.Fromastructuralpointofview，acolumnisamemberthatresiststhelateralforcemainlybyflexureactionwhereasapierisamemberthatresiststhelateralforcemainlybyashearmechanism.Apierthatconsistsofmultiplecolumnsisoftencalledabent.上一页下一页返回Unit4—4PiersandColumnsThereareseveralwaysofdefiningpiertypes.Oneisbyitsstructuralconnectivitytothesuperstructure:monolithicorcantilevered.Anotherisbyitssectionalshape:solidorhollow;round，octagonal，hexagonal，orrectangular.Itcanalsobedistinguishedbyitsframingconfiguration:singleormultiplecolumnbent;hammerheadorpierwall.上一页下一页返回Unit4—4PiersandColumnsSelectionCriteriaSelectionofthetypeofpiersforabridgeshouldbebasedonfunctional，structural，andgeometricrequirements.Aestheticsisalsoaveryimportantfactorofselectionsincemodernhighwaybridgesarepartofacity'slandscape.Fig.1showsacollectionoftypicalcrosssectionshapesforovercrossingsandviaductsonlandandFig.2showssometypicalcrosssectionshapesforpiersofriverandwaterwaycrossings.Piertypesareoftenmandatedbygovernmentagenciesorowners.上一页下一页返回Unit4—4PiersandColumnsManystatedepartmentsoftransportationintheUnitedStateshavetheirownstandardcolumnshapes.Solidwallpiers，asshowninFig.3(a)andFig.4，areoftenusedatwaterwaycrossingssincetheycanbeconstructedtoproportionsthatareberthslenderandstreamlined.Thesefieatureslendthemselveswellforprovidingminimalresistancetofloodflows.上一页下一页返回NewWordsandExpressionsbent n.排架overcrossing n.上跨交又;立交桥viaduct n.高架桥seismicevent地震事件Iateralload横向荷载theductilityaspect延展性能reinforcedconcrete钢筋混凝土lowseismicarea低烈度区froma…pointofview从……角度看上一页下一页返回NewWordsandExpressionsselectioncriteria选择标准spacelimitation空间的局限性precastprestressedconcretesuperstructure预制的预应力混凝土上部结构columnbentpier排柱式桥墩capbeam盖梁supportingcolumn支撑柱上一页下一页返回NewWordsandExpressionscast-in-placeconstruction现浇施工byfar到目前为止pilepier桩式桥墩drilledshaft钻孔灌注桩dependuponrivercrossing跨越河流multiplepile群桩slabbridge板桥上一页下一页返回ExercisesI.Fillintheblankswithchangingtheformwhenthesuitablewordsorexpressionsfromthelistgivenbelow，necessary.mandateformsubstructurecapbase1.Pierisusuallyusedasageneraltermforanytypeof_____locatedbetweenhorizontalspansandfoundations.2.Selectionofthetypeofpiersforabridgeshouldbe_____onfunction,structural,andgeometricrequirements.上一页下一页返回Exercises3.Piertypesareoften___bygovernmentagenciesorowners.4.Acolumnbentpierconsistsofa___beamandsupportingcolumns___aframe.II.AnswerthefollowingquestionsinEnglish.1.Whichistheselectioncriteriaofthetypeofpiersforabridge?2.Howmanywaysaretheretodefinepiertypes?上一页下一页返回ExercisesIII.TranslatethefollowingsentencesintoChinese.1.Piersprovideverticalsupportsforspansatintermediatepointsandperformtwomainfunctions:transferringsuperstructureverticalloadstothefoundationsandresistinghorizontalforcesactingonthebridge.上一页下一页返回Exercises2.Apileextensionpierconsistsofadrilledshaftasthefoundationandthecircularcolumnextendedfromtheshafttoformthesubstructure.Anobviousadvantageofthistypeofpieristhatitoccupiesaminimalamountofspace.Wideninganexistingbridgeinsomeinstancesmayrequirepileextensionsbecauselimitedspaceprecludestheuseofothertypesoffoundations上一页返回Unit4—5TunnelEngineeringAtunnelismuchmorethanjustatunnel.Itservesanyofmyriadfunctions--highway，railroad，orrapidtransitartery;pedestrianpassageway;fleshwaterconveyance，coolingwatersupply;wastewatercollectorortransport;hydropower;inlong，prefabricatedsectionssunkinplaceasinimmersedtubes;inshortprefabricatedsectionspushedintoplacefromjackingpits;bydrillingorblasting;bymechanizedmeanssuchastunnelboringmachines(fig.1)orcontinuousminersroadheaderswiththeaidofaprotectiveshieldinfreeorcompressedair;下一页返回Unit4—5TunnelEngineeringandtheywilleventuallybeconstructedinwaysnowexistingonlyinourimaginations.Incrosssectionittakesoneofseveralshapescircularmulticurve，horseshoe，arched，orflat-roofed，andwithclearspansoffirmaflewfleetmirethan50fitandincavernfirm.muchwider.Itslengthcanvaryfromlessthan100fttomorethan30miles.Atunnelcanbelocatedinanyofavarietyofplacesundermountainscitiesriverslakesseaestuariesstraitsorbays.Finally，atunnelisconstructedinoneofinnumerablemediasoftground，mixedface(Fig.2)，rockuniform，jumbled，layered，drywetstable.上一页下一页返回Unit4—5TunnelEngineeringMostofall.atunnelexistsbecausethereisdemonstratedneed—tomovepeopleormaterialwherenoothermeansispracticaloradequate，ortoaccomplishtherequiredmovementmoredirectly，morequickly，ormoresafely.Theneedmaybeforstorage，eithershorttermasforstorageofstormwaterflowstoreducetheotherwisehighpeakcapacitiesrequiredofwastewatertreatmentplants，orlongertermasforstorageofvitalrawmaterialorproducts.上一页下一页返回Unit4—5TunnelEngineeringAtunnelalsoismorethanaholeinthegroundtoprovideforadesiredmovementofpeopleormaterial.Toaccomplishthemovementsatisfactorilyoneormoreofavarietyoffacilitiesinsimpleorcomplexformmustbeprovidedinadditiontothecontinuousspace.Themostobviousneedforhighwaytunnelisventilation.Freshairmustbesuppliedinproportiontotunnelusage.Theairalsomustbeofreasonablepuritythisrequiresconstantmonitoringforpollutantsandconsequentadjustmentoftheairsupplyandexhaust.上一页下一页返回Unit4—5TunnelEngineeringAnotheressentialforhighwaytunnelissomeformanddegreeoflighting.Inlow-useruraltunnel，thevehicles'headlightsmaysuffice.Inhigh-use(generallyurban)tunnels，asophisticatedsystemofhigh-leveladjustablelightingisnecessarybothforsafetyandforensuringmaximumappropriatespeeds.上一页下一页返回Unit4—5TunnelEngineeringWhileventilationandlightingarethemostobviousofday-to-daytunneloperationalneeds，thereisagreaterneed.Thatthisneed