外文翻译--道路设计.doc

1附录A外文翻译原文RoadDesignHistoryofRoadDesignFirstlyletmeapologiseforthispage.ItislargelytextbasedduetothenatureofitandifreadingisdifficultthenIamsorry.Thisisduesolelytothematerialcoveredandistheonlypageintheseries.Thisisnottypicalastheresthavegraphicsorimagestokeepyouamused.SecondlythispageisverymuchahistoryofroadbuildingintheUnitedKingdomThefirstroadbuildersofanysignificanceinWesternEuropeweretheRomans,whosawtheabilitytomovequicklyasessentialforbothmilitaryandcivilreasons.ItisfromtheRomansthatthetermhighwaycomesasalltheirroadswereelevated1mabovethelocalleveloftheland.Thiswastominimisetheriskofanambush,aswasthebestknowncharacteristicoftheroads,theirlackofcorners.ThestandardssetbytheRomansintermsofdurabilityfarexceededanythingachievedafterthefalloftheempire.TheRomanapproachtoroaddesignisessentiallythesameasthatincurrentuse.Theroadswereconstructedofseveraldifferentlayers,increasinginstrengthfromthebottom.Thelowestlayerwasnormallyarubble,intermediatelayersweremadeoflimeboundconcreteandtheupperlayerwasaflagorlimegroutedstoneslabs.Thethicknessofthelayerswasvariedaccordingtothelocalgroundconditions.AfterthefalloftheRomanEmpiretheroadsystemfellintoastateofdisrepairandbytheendofthemiddleages,therewasineffectnoroadsysteminthecountry.Theonlyroutesavailablewereunpavedtracks,muddyandimpassableinwinteranddustyandimpassableinsummer.Diversionsaroundparticularlypoorstretchesresultedinsinuousalignments.Thestateoftheroadscombinedwiththegenerallawlessnessatthetimemeantonlythedeterminedorinsanetraveled.Thefirstchangeinthisattitudecamein1555whenanActofParliamentwaspassedimposingadutyonallparishestomaintainitsroads.AlsoincludedintheActwasthecreationofthepositionofaSurveyorofHighways.Thiswasunpaidandunderresourcedthoughandwhencombinedwiththelackoftechnicalskillsitisnosurprisethatthepostbecamedistinctlyunpopularandineffective.2Thislackofresourcesmeantthatthefirstmajorroadwasnotestablisheduntilthelatterpartoftheseventeenthcentury.Theseroadswereknownasturnpikeroadswheretheroaduserpaidatoll.ThefirstsectionswereknownastheGreatNorthRoadandhassincebecometheA1trunkroad.InthefollowingcenturyTurnpikeTrustswereestablishedtoprovideturnpikeroadsalongmajorroutesintheUnitedkingdom.InthisimprovedfinancialclimateroadbuildingtechniquesevolvedthankstotheworkofpioneerssuchasTelfordandMacadam.Byabout1830asystemofwellpavedbuiltroadsexistedsuchthattheonlyconstraintsonroadtrafficandtraveltimeswereimposedbythenatureofroadvehicles.Thenextimprovementcameaboutwiththeadventoftherailways.Withrapidtransportbetweentownsnowpossible,theturnpikesbecameuneconomicalandwhilstroadbuildingintownscontinuedapacetheturnpiketrustscollapsed.Legislationinthelate19thcenturysetthesceneforthecurrentadministrativearrangementsforhighwayconstructionandmaintenancebutthetechnologyremainedprimitiveandempirical.Onlyinrecentyearshasthatsituationimprovedtoanyextentandevennowmostroaddesignisbasedonempiricalrelationshipsandexperimentalwork.Thepresentsituationisalmostacompletereversal,withfundingfornewroadscomingfromtheprivatesector.Inexchangeforbuildingandmaintainingtheroadtheownersarepaidatollbythegovernmentforeachvehicleusingtheroad,asortofmodernturnpikesystem.TrafficAnalysisRoadloadingtakesmanydifferentforms,fromabicycletomulti-axledtruckandtrailercombinations.TrafficAnalysiscanbesplitintotwowelldefinedareas:TrafficVolume-ThisistheroleoftheTrafficEngineeranddoesnotnormallyconcerntheCivilEngineer.Thisisnotrelevanttodeterminingtheloadontheroad,onlythesizeandlayout.TrafficLoading-ThisistheroleofthePavementEngineerandinvolvesdeterminingtheloadingontheroadtobecarriedforwardtothePavementDesign.TrafficVolume3Theroleofthetrafficengineeristoenablealltraffictotravelontheroadatareasonablespeedandwithanappropriatedegreeofsafety.ThisisnottheloadingthatisusedinthePavementDesign.Thesevaluesareusedtodeterminetheroadwidthonly.Withrelationtothevolumeoftrafficusingtheroad,thepassengercarisadoptedasthestandardunitandothervehiclesareassessedintermsofpassengercarunits(pcu).Differencesintheurbanandruralsituationsariseduetothevariationofspeedsinthetwoareas.Decisionsonroadwidtharenotnormallymadeontotaltrafficflowperdayasthisismisleadingbutratheronthepeakhourlyflow.InBritainthemaximumpermissibleflowis3,000pcu/hforatwolanedualcarriagewayand4,500pcu/hforathreelanedualcarriageway(motorway).Forallpurposeroadswithjunctionsthesefiguresreduceto1,100and1,900pcu/hrespectively.Wheretheroadisnew,studiesmustbecarriedouttoestimatethevolumeoftrafficexpectedtousetheroad.Wherethenewroadreplacesexistingroadsthisisnottoodifficult.Ifhowevertheroadisexpectedtochangetheflowoftrafficthenanalysisshouldbecarriedoutastothevolumeandconstitutionoftrafficonthenewroad.Mattersarefurthercomplicatediftheroadisverylongorprovidesaccesstoorfromalargetown.Computermethodsarenowavailabletoaidinthisprocess.Theconstitutionoftrafficonthenewroadisofinteresttothepavementengineer.TrafficLoadingInthissection,wewilldiscussthetrafficloadingthatistakenforwardtothepavementdesignsection.UnlikeintheabovesectionwherePassengerCarUnitswerethereferenceunit,wewillworkinStandardAxles.Thisisareferenceunittodeterminetheaverageloadingonapavementbywhatisknownasthestandardaxle.Thisthenallowsatotalloadingoverthelifeofthepavementtobedetermined,normallyinMillionsofStandardAxles(msa).EarthworksTheProcessofearthworksistoexcavatetheexistinglandtoasuitablelevelsothatroadconstructionmaybegin.Theearthworkscantaketheformofeitherexcavationintheformofcutsortheconstructionofembankmentstocarryan4elevatedhighway.Normallyinaroaddesignproject,bothwillbenecessaryandmovementofearthfromonepartofthesitetothenextwillbenecessary.Thisshouldbedonewithaslittlewastecreatedoraslittleextramaterialrequiredasdisposalorcollectionisexpensive.Alsoincludedunderthetopicofearthworksisthecompactionoftheroadmaterialstotheappropriatelevel.Thishoweverisnotcoveredasitismoreconcernedwiththeactualconstructionoftheroadthanthedesignofit.Thispageisconcernedsolelywiththedesignoftheearthworksandnotwiththeactualdesignoftheembankmentsorcuts.Ifyouwishtolearnmoreaboutthisthenlinkstorelevantpagesarecontainedinthegeotechnicalsectionofthelinkspage.Alinktothiscanbefoundopposite.Ofthetopicscoveredinthispage,theycanbesplitupintothedesignoftheearthworksandtheplantusedintheconstruction.ExcavationThemostimportantfeatureoftheexcavationisthematerialyouareworkingwith.ThiswillbeknownfromtheSiteInvestigation.Poorinformationcanleadtotechnicalproblemsandtocostoverruns.Therearemanywaysofclassifyingthesoilintermsofitseaseofexcavationincludingseismictechniq