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路基路面专业英语Lesson3RoadConstruction(道路施工)Lesson5Pavement(路面)Lesson6BituminousMaterialsandPavements(沥青材料和沥青路面)Lesson8PavementMaintenanceandStrengthening(路面养护与补强)Lesson3RoadConstruction(道路施工)图一道路施工RoadConstruction(道路施工)Roadbedsunderlie(v.在下面,作为基础)highwaypavementstructuresandtheballast(n.道渣,石渣)andtrackonwhichtrainsmove.Unlessthereisabridge,tunnel,orotherspecialstructure,thisroadbedisconstructedofin-situsoilsoronearthembankments.Buildingitisthefirststepinproduc-ingafinishedfacility.SiteClearing(清场)Clearingthesiteprecedesallgradingandmostothercon-structionoperations.Siteclearinginruralareasmaysometimesmerelyrequirethatgrass,shrubs,andotherplantsorcropsberemoved.How-ever,itsome-timescaninvolveremovingtreesandtreestumps(n.树桩)anddisposingofthedebris(n.碎屑片,堆积层).Theacceptedprocedureistoremovepracticallyallvegetablematterfromtheoriginalgroundandfromfillmaterial,since,ifallowedtoremain,itmaydecayandleavevoidsthatresultinsettlement.Selectiveclearinginadjoiningareasmayattimesberequired.ExcavationExcavationistheprocessoflooseningandremovingearthorrockfromitsoriginalpositioninacutandtransportingittoafillortoawastedeposit(弃土堆).Selectionofequipmentdependsonthenatureofthematerial,howfaritistobemoved(hauled),andthemethodofdisposal.Materialsareusuallydescribedas‘rock,’‘looserock,’or‘common,’with‘common’signifyingallmaterialnototherwiseclassified.Rock,sometimescalled“solidrock,”nearlytotrucksorotherhaulingunits.Blastedrockmaybemovedordriftedforshortdistancesbymeansofabulldozer(n.推土机),whichis,ineffect,ahugetractor-mountedblade.Looserockincludesmaterialssuchasweatheredorrottenrock(风化岩),orearthmixedwithboulders(n.孤石,粗砾),andoftenisdugwithloadersorshovelswithoutanypreviousblasting.Attines,however,furtherlooseningbyblastingmaypermitfasterloadinganddecreaseequipmentwear,withanattendant(a.伴随的)reductionintotalcost.Loadersandshovelseasilydigcommonexcavationwithoutblasting.Inrecentyearslargerippers(n.松土机)mountedonhugecrawler(n.履带)tractorsandpushedbyoneormoreaddedtractorshavebeenusedsuccessfullytobreakuplooseorfractured(v.破裂,断裂)rock.Theloosenedrockisthenhandledbytractor-scraper(拖式铲运机)unitsasisdonewith“common”excavation.Gradingproceduresin“common”orearthexcavationaregovernedbycost.Wherematerialismovedlessthanabout200ft(60m)orsteeplydownhill,driftingwithatrackorwheeltypebulldozer(履带式或轮式推土机)ischeapest.Formoderateandlongerhauls,self-loadingscrapers(自载铲运机)pulledbyrubber-tiredhaulingunitsandpush-loaded(推式铲运机)bytractorsofferlowercosts.Sometimesitismoreeconomicalforscraperstoself-loadbyattachinglong,power-drivenbladesthatpullthedirtintothescraperbowl.Forhaulsofconsiderablelengthoroverthepublichighwayswhereaxleloadsarelimited,rear-dumptrucks(后卸式货车)orbottom-dumptrucks(底卸式货车)loadedbyfront-endloaders(前端装载机),powershovels(挖土机),orbeltconveyorsmaybecheapest.Attimes,weathermaybeacontrollingfactor.Forexample,therubber-tiredtractorunitshavedifficultyinoperatingonwet,slipperyroadbeds.Thus,inareassubjecttoheavyrainstorms,scraperspulledbytrack-typetractorsmaybemoresatisfactory.Earthmoving(n.运土)hasundergonearevolutionsince1925,whenthemostusedtoolwasascraperof1/2yd3(0.4m3)orlesscapacitypulledbytwoorfourhorsesormules.Forexample,combinationsof15-yd3(11m3)loadersand125-tontrucksarenowemployed.Scraperswith32-yd3(24m3)struckcapacity(平斗容量)aremarketedwithasecondenginemountedontherearofthescrapertosupplyaddedtractiveforce.Aunitwiththeaddedengineontherear,providesatotalof950hp(700km).Iftwoofthe410hp(300km)pushertractorsareaddedforloading,atotalof1770hp(1300kw)isbroughttobear.Severalothermanufacturersmakecomparableequipment.Inatlestoneinstance,a100-yd3(76m3)scraperhasbeenused.Somefeelthatthe“size”revolutioninearthmovingequipmentisover,exceptinspecialsituations.Theypointtothedecreasednumberoflargegradingcontracts,highinvestmentcosts,andthedifficultyintran-sportingsuchlargemachinesfromprojecttoproject.Therearemanyvariablesinearthmovingsuchasthesizeandcomplexityoftheproject,thenatureofthematerial,climaticconditions,andtheskillandknowledgeofequipmentoperatorsandsupervisors(n.管理者,监督者).Forthisreason,therearenoeasyanswersonequipmentselection.EmbankmentTheterm“embankment”describesthefilladdedabovethelowpointsalongtheroadwaytoraisetheleveltothebottomofthepavementstructure.Materialforembankmentcommonlycomesfromroadwaycutsordesignatedborrowareas(借土区).Modernpracticerequiresthatembankmentconstructionbecarefullyexecutedandcontrolled.Atonetime,fills,whetherofrockorearth,wereconstructedtofullheightby“end-dumping”fromthetransportingvehicle.Inthisprocedurethematerialslidorrolledintoplacedownthefaceoftheprogressingfill.Noattemptwasmadetocontrolmoisturecontent(含水量,湿度)ortosecurecompaction.Itwasanticipated(v.预期,预测)thatsuchfillswouldsettleforsometimeandthatinitialpavement,ifany,wastemporary.Constructionofpavementoverhighfillsoftenwasdeferred(v.推迟,延期)forayearormoreaftercompletionofthefilltoallowthissettlementtooccur.Inthe1930sengineersfoundthatsuperiorembankmentscouldbeconstructedbyspreadingthematerialinrelativelythinlayersandcompactingitatamoisturecontentclosetooptimum.Theimprovementresultedlargelybe