土木工程专业外文翻译道路设计.docx
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土木工程专业外文翻译道路设计.docx
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土木工程专业外文翻译道路设计
RoadDesign
HistoryofRoadDesign
Firstlyletmeapologiseforthispage.ItislargelytextbasedduetothenatureofitandifreadingisdifficultthenIamsorry.Thisisduesolelytothematerialcoveredandistheonlypageintheseries.Thisisnottypicalastheresthavegraphicsorimagestokeepyouamused.SecondlythispageisverymuchahistoryofroadbuildingintheUnitedKingdom.
ThefirstroadbuildersofanysignificanceinWesternEuropeweretheRomans,whosawtheabilitytomovequicklyasessentialforbothmilitaryandcivilreasons.ItisfromtheRomansthatthetermhighwaycomesasalltheirroadswereelevated1mabovethelocalleveloftheland.Thiswastominimisetheriskofanambush,aswasthebestknowncharacteristicoftheroads,theirlackofcorners.ThestandardssetbytheRomansintermsofdurabilityfarexceededanythingachievedafterthefalloftheempire.
TheRomanapproachtoroaddesignisessentiallythesameasthatincurrentuse.Theroadswereconstructedofseveraldifferentlayers,increasinginstrengthfromthebottom.Thelowestlayerwasnormallyarubble,intermediatelayersweremadeoflimeboundconcreteandtheupperlayerwasaflagorlimegroutedstoneslabs.Thethicknessofthelayerswasvariedaccordingtothelocalgroundconditions.
AfterthefalloftheRomanEmpiretheroadsystemfellintoastateofdisrepairandbytheendofthemiddleages,therewasineffectnoroadsysteminthecountry.Theonlyroutesavailablewereunpavedtracks,muddyandimpassableinwinteranddustyandimpassableinsummer.Diversionsaroundparticularlypoorstretchesresultedinsinuousalignments.Thestateoftheroadscombinedwiththegenerallawlessnessatthetimemeantonlythedeterminedorinsanetraveled.
Thefirstchangeinthisattitudecamein1555whenanActofParliamentwaspassedimposingadutyonallparishestomaintainit'sroads.AlsoincludedintheActwasthecreationofthepositionofaSurveyorofHighways.Thiswasunpaidandunderresourcedthoughandwhencombinedwiththelackoftechnicalskillsitisnosurprisethatthepostbecamedistinctlyunpopularandineffective.
Thislackofresourcesmeantthatthefirstmajorroadwasnotestablisheduntilthelatterpartoftheseventeenthcentury.Theseroadswereknownasturnpikeroadswheretheroaduserpaidatoll.ThefirstsectionswereknownastheGreatNorthRoadandhassincebecometheA1trunkroad.InthefollowingcenturyTurnpikeTrustswereestablishedtoprovideturnpikeroadsalongmajorroutesintheUnitedkingdom.InthisimprovedfinancialclimateroadbuildingtechniquesevolvedthankstotheworkofpioneerssuchasTelfordandMacadam.Byabout1830asystemofwellpavedbuiltroadsexistedsuchthattheonlyconstraintsonroadtrafficandtraveltimeswereimposedbythenatureofroadvehicles.
Thenextimprovementcameaboutwiththeadventoftherailways.Withrapidtransportbetweentownsnowpossible,theturnpikesbecameuneconomicalandwhilstroadbuildingintownscontinuedapacetheturnpiketrustscollapsed.Legislationinthelate19thcenturysetthesceneforthecurrentadministrativearrangementsforhighwayconstructionandmaintenancebutthetechnologyremainedprimitiveandempirical.Onlyinrecentyearshasthatsituationimprovedtoanyextentandevennowmostroaddesignisbasedonempiricalrelationshipsandexperimentalwork.
Thepresentsituationisalmostacompletereversal,withfundingfornewroadscomingfromtheprivatesector.Inexchangeforbuildingandmaintainingtheroadtheownersarepaidatollbythegovernmentforeachvehicleusingtheroad,asortofmodernturnpikesystem.
TrafficAnalysis
Roadloadingtakesmanydifferentforms,fromabicycletomulti-axledtruckandtrailercombinations.
TrafficAnalysiscanbesplitintotwowelldefinedareas:
TrafficVolume-ThisistheroleoftheTrafficEngineeranddoesnotnormallyconcerntheCivilEngineer.Thisisnotrelevanttodeterminingtheloadontheroad,onlythesizeandlayout.
TrafficLoading-ThisistheroleofthePavementEngineerandinvolvesdeterminingtheloadingontheroadtobecarriedforwardtothePavementDesign.
TrafficVolume
Theroleofthetrafficengineeristoenablealltraffictotravelontheroadatareasonablespeedandwithanappropriatedegreeofsafety.ThisisnottheloadingthatisusedinthePavementDesign.Thesevaluesareusedtodeterminetheroadwidthonly.
Withrelationtothevolumeoftrafficusingtheroad,thepassengercarisadoptedasthestandardunitandothervehiclesareassessedintermsofpassengercarunits(pcu).
Differencesintheurbanandruralsituationsariseduetothevariationofspeedsinthetwoareas.Decisionsonroadwidtharenotnormallymadeontotaltrafficflowperdayasthisismisleadingbutratheronthepeakhourlyflow.InBritainthemaximumpermissibleflowis3,000pcu/hforatwolanedualcarriagewayand4,500pcu/hforathreelanedualcarriageway(motorway).Forallpurposeroadswithjunctionsthesefiguresreduceto1,100``and1,900pcu/hrespectively.
Wheretheroadisnew,studiesmustbecarriedouttoestimatethevolumeoftrafficexpectedtousetheroad.Wherethenewroadreplacesexistingroadsthisisnottoodifficult.Ifhowevertheroadisexpectedtochangetheflowoftrafficthenanalysisshouldbecarriedoutastothevolumeandconstitutionoftrafficonthenewroad.Mattersarefurthercomplicatediftheroadisverylongorprovidesaccesstoorfromalargetown.Computermethodsarenowavailabletoaidinthisprocess.Theconstitutionoftrafficonthenewroadisofinteresttothepavementengineer.
TrafficLoading
Inthissection,wewilldiscussthetrafficloadingthatistakenforwardtothepavementdesignsection.UnlikeintheabovesectionwherePassengerCarUnitswerethereferenceunit,wewillworkinStandardAxles.Thisisareferenceunittodeterminetheaverageloadingonapavementbywhatisknownasthestandardaxle.Thisthenallowsatotalloadingoverthelifeofthepavementtobedetermined,normallyinMillionsofStandardAxles(msa).
Earthworks
TheProcessofearthworksistoexcavatetheexistinglandtoasuitablelevelsothatroadconstructionmaybegin.Theearthworkscantaketheformofeitherexcavationintheformofcutsortheconstructionofembankmentstocarryanelevatedhighway.Normallyinaroaddesignproject,bothwillbenecessaryandmovementofearthfromonepartofthesitetothenextwillbenecessary.Thisshouldbedonewithaslittlewastecreatedoraslittleextramaterialrequiredasdisposalorcollectionisexpensive.
Alsoincludedunderthetopicofearthworksisthecompactionoftheroadmaterialstotheappropriatelevel.Thishoweverisnotcoveredasitismoreconcernedwiththeactualconstructionoftheroadthanthedesignofit.
Thispageisconcernedsolelywiththedesignoftheearthworksandnotwiththeactualdesignoftheembankmentsorcuts.Ifyouwishtolearnmoreaboutthisthenlinkstorelevantpagesarecontainedinthegeotechnicalsectionofthelinkspage.Alinktothiscanbefoundopposite.
Ofthetopicscoveredinthispage,theycanbesplitupintothedesignoftheearthworksandtheplantusedintheconstruction.
Excavation
Themostimportantfeatureoftheexcavationisthematerialyouareworkingwith.ThiswillbeknownfromtheSiteInvestigation.Poorinformationcanleadtotechnicalproblemsandtocostoverruns.
Therearemanywaysofclassifyingthesoilintermsofit'seaseofexcavationincludingseismictechniques.ThemostcommonintheUnitedKingdomatpresenthoweveristheEaseofDiggingscaleordiggability.Thisclassifiesthesoilinoneoffourcategories:
EEasydigging-Loosefreerunningsoilsegsands,finegravels.
MMedium-Densercohesivesoilsegclayeygravel,lowPIclays.
M-HMediumtoHard-egbrokenrock,wetheavyclay,gravelwithboulders.
HHard-materialrequiringblastingandhardhighPIclays.
TypicaldiggabilityfactorscanbeseeninTable1below.
Anotherimportantfeatureofrockistheamountoffissuring.Therearetwomethodsofassessingthis,thepercentageRockQualityDatamethodandtheSpacingofjointsmethod.Eachoftheseleadsdirectlytoanestimateoftheuniaxialcompressivestrengthandthusanindicationoftheexcavationmethod.BoththesecanbefoundintheManualofcontractsdocument,Series6001.
Excavationincreasesthevolumeofmaterial.Itisthereforenecessarytouseabulkingfactortodeterminethevolumeofmaterialthatwillbecreatedbyexcavation.Bulkingfactorisdefinedas:
BulkingFactor=VolumeafterExcavation/VolumebeforeExcavation
Similarlyashrinkagefactorisdefinedforthecompactionofasoilatit'sfinaldestination.:
ShrinkageFactor=VolumeafterCompaction/VolumebeforeExcavation
Inadditiontotheaboveproperties,itisimportanttohavesomeideaaboutthetrafficabilityofthesoils.Thisisbecausetheexcavationplantwillneedtodriveoverthesoilswithoutbecomingboggeddown.Thetrafficabilityofthesoilsisrelatedtotheirdrainageproperties.
Sands/Gravels
FreeDraining.Tendtohavefewproblems.
HighPIClays
Lowpermeabilitywillpreventwateringresssothesurfacebecomesdangerousbutnotinthelongterm.
Silts/LowPIClays
Thesecausethemostproblems.Permeabilityallowsingresswhichsoftensthesoilsthusweakeningthem.
AsphaltPavingOperation
Introduction
Thesubjectofthistermprojectwasanasphaltpavingprocessutilizingapavingmachineand20tonscapacitytri-axletrucks.ThelocationoftheprocesswasatthecornerofMainandMadisoninGreenwood(SouthofIn
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