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外文翻译--道路设计.doc

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外文翻译--道路设计.doc

1附录A外文翻译原文RoadDesignHistoryofRoadDesignFirstlyletmeapologiseforthispage.ItislargelytextbasedduetothenatureofitandifreadingisdifficultthenIamsorry.Thisisduesolelytothematerialcoveredandistheonlypageintheseries.Thisisnottypicalastheresthavegraphicsorimagestokeepyouamused.SecondlythispageisverymuchahistoryofroadbuildingintheUnitedKingdom.ThefirstroadbuildersofanysignificanceinWesternEuropeweretheRomans,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,fromabicycletomultiaxledtruckandtrailercombinations.TrafficAnalysiscanbesplitintotwowelldefinedareasTrafficVolumeThisistheroleoftheTrafficEngineeranddoesnotnormallyconcerntheCivilEngineer.Thisisnotrelevanttodeterminingtheloadontheroad,onlythesizeandlayout.TrafficLoadingThisistheroleofthePavementEngineerandinvolvesdeterminingtheloadingontheroadtobecarriedforwardtothePavementDesign.TrafficVolume3Theroleofthetrafficengineeristoenablealltraffictotravelontheroadatareasonablespeedandwithanappropriatedegreeofsafety.ThisisnottheloadingthatisusedinthePavementDesign.Thesevaluesareusedtodeterminetheroadwidthonly.Withrelationtothevolumeoftrafficusingtheroad,thepassengercarisadoptedasthestandardunitandothervehiclesareassessedintermsofpassengercarunitspcu.Differencesintheurbanandruralsituationsariseduetothevariationofspeedsinthetwoareas.Decisionsonroadwidtharenotnormallymadeontotaltrafficflowperdayasthisismisleadingbutratheronthepeakhourlyflow.InBritainthemaximumpermissibleflowis3,000pcu/hforatwolanedualcarriagewayand4,500pcu/hforathreelanedualcarriagewaymotorway.Forallpurposeroadswithjunctionsthesefiguresreduceto1,100``and1,900pcu/hrespectively.Wheretheroadisnew,studiesmustbecarriedouttoestimatethevolumeoftrafficexpectedtousetheroad.Wherethenewroadreplacesexistingroadsthisisnottoodifficult.Ifhowevertheroadisexpectedtochangetheflowoftrafficthenanalysisshouldbecarriedoutastothevolumeandconstitutionoftrafficonthenewroad.Mattersarefurthercomplicatediftheroadisverylongorprovidesaccesstoorfromalargetown.Computermethodsarenowavailabletoaidinthisprocess.Theconstitutionoftrafficonthenewroadisofinteresttothepavementengineer.TrafficLoadingInthissection,wewilldiscussthetrafficloadingthatistakenforwardtothepavementdesignsection.UnlikeintheabovesectionwherePassengerCarUnitswerethereferenceunit,wewillworkinStandardAxles.Thisisareferenceunittodeterminetheaverageloadingonapavementbywhatisknownasthestandardaxle.Thisthenallowsatotalloadingoverthelifeofthepavementtobedetermined,normallyinMillionsofStandardAxlesmsa.EarthworksTheProcessofearthworksistoexcavatetheexistinglandtoasuitablelevelsothatroadconstructionmaybegin.Theearthworkscantaketheformofeitherexcavationintheformofcutsortheconstructionofembankmentstocarryan4elevatedhighway.Normallyinaroaddesignproject,bothwillbenecessaryandmovementofearthfromonepartofthesitetothenextwillbenecessary.Thisshouldbedonewithaslittlewastecreatedoraslittleextramaterialrequiredasdisposalorcollectionisexpensive.Alsoincludedunderthetopicofearthworksisthecompactionoftheroadmaterialstotheappropriatelevel.Thishoweverisnotcoveredasitismoreconcernedwiththeactualconstructionoftheroadthanthedesignofit.Thispageisconcernedsolelywiththedesignoftheearthworksandnotwiththeactualdesignoftheembankmentsorcuts.Ifyouwishtolearnmoreaboutthisthenlinkstorelevantpagesarecontainedinthegeotechnicalsectionofthelinkspage.Alinktothiscanbefoundopposite.Ofthetopicscoveredinthispage,theycanbesplitupintothedesignoftheearthworksandtheplantusedintheconstruction.ExcavationThemostimportantfeatureoftheexcavationisthematerialyouareworkingwith.ThiswillbeknownfromtheSiteInvestigation.Poorinformationcanleadtotechnicalproblemsandtocostoverruns.Therearemanywaysofclassifyingthesoilintermsofitseaseofexcavationincludingseismictechniques.ThemostcommonintheUnitedKingdomatpresenthoweveristheEaseofDiggingscaleordiggability.ThisclassifiesthesoilinoneoffourcategoriesEEasydiggingLoosefreerunningsoilsegsands,finegravels.MMediumDensercohesivesoilsegclayeygravel,lowPIclays.MHMediumtoHardegbrokenrock,wetheavyclay,gravelwithboulders.HHardmaterialrequiringblastingandhardhighPIclays.TypicaldiggabilityfactorscanbeseeninTable1below.Anotherimportantfeatureofrockistheamountoffissuring.Therearetwomethodsofassessingthis,thepercentageRockQualityDatamethodandtheSpacingofjointsmethod.Eachoftheseleadsdirectlytoanestimateoftheuniaxialcompressivestrengthandthusanindicationoftheexcavationmethod.BoththesecanbefoundintheManualofcontractsdocument,Series6001.

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