路面设计外文翻译柔性路面设计.docx

路面设计外文翻译柔性路面设计.docx

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路面设计外文翻译柔性路面设计

英文翻译

Flexiblepavementdesign

Generallyspeaking,pavements（andbases）maybedividedintotwobroadclassificationsortipes:

rigidandflexible.AscommonlyusedintheUnitedStates,theterm“rigidpavement”isappliedtowearingsurfacesconstructedofPortland-cementconcrete.Apavementconstructedofconcreteisassumedtopossessconsiderableflexuralstrengththatwillpermitittoactasabeamandallowittobridgeoverminorirregularitieswhichmayoccorinthebaseorsubgradeonwhichitrests;hencetheterm“rigid”.Similarity,aconcretebasethatsupportsabrickorblocklayermightbedescribedas“rigid”.

Allothertypesofpavementhavetraditionallybeenclassedas“flexible”.Acommonlyuseddefinitionisthat“aflexiblepavementisastructurethatmaintainscontactwithanddistributesloadstothesubgradeanddependsonaggregateinterlock,particlefriction,andcohesionforstability”.Thus,theclassicalflexiblepavementincludeprimarilythosepavementthatarecomposedofaseriesofgranularlayerstoppedbyarelativelythinhigh-qualitybituminouswearingsurface.Typically,thehighest-quatilymaterialsareatornearthesurface.Itshouldbepointedoutthatcertainpavementsthathaveanasphaltsurfacemaybehavemoreliketheclassical“rigid”pavement,forexample,pavementthathaveverythickasphaltsurfaceorthathavebasecoursescomposedofaggregatetreatedwithasphalt,cement,orlime-flyash.However,forconvenienceofpresentation,thesepavementswillbeconsideredtobeintheflexibleclass.

Thestructureofflexiblepavementiscomposedofa“wearingsurface”,base,subbase（notalwaysused）,andsubgrade.Thewearingsurfaceandthebaseoftencomprisetwoormorelayersthataresomewhatdifferentincompositionandthatareputdowninseparateconstructionoperations.Onmanyheavy-dutypavements,asubbaseofselectmaterialisoftenplacedbetweenthebaseandsubgrade.thewearingsurfacemayrangeinthicknessfromlessthan1in.inthecaseofabituminoussurfaceusedforlow-cost,light-trafficloadsto6in.ormoreofalphaltconcreteusedforheavilytraveledroutes.Thewearingsurfacemustbecapableofwithstandingthewearandabrasiveeffectsofmovingvehiclesandmustpossesssufficientstabilitytopreventitfromshovingandruttingundertrafficloads.Inaddition,itservesausefulpurposeinpreventingtheentranceofexcessivequantitiesofsurfacewaterintothebasesubgradefromdirectlyabove.

Thebaseisalayer（orlayers）ofveryhighstabilityanddensity.Itsprinciplepurposeistodistributeor“spread”thestressescreatedbywheelloadsactingonthewearingsurfacesothatthestressestransmittedtothesubgradewillnotbesufficientlygreattoresultinexcessivedeformationordisplacementofthatfoundationlayer.Thebasemustalsobeofsuchcharacterthatitisnotdamagedbycapillarywaterand/orfrostaction.Locallyavailablematerialsareextensivelyusedforbaseconstruction,andmaterialspreferredforthistypeofconstructionvarywwidelyindifferentsectionsofthecountry.Forexample,thebasemaybecomposedofgravelorcrushedrockoritmaybaeagranularmaterialtreatedwithasphalt,cement,orlime-flyashstabilizingagents.

Asubbaseofgranularmaterialorstabilizedmaterialmaybeusedinareaswherefrostactionissevere,inlocationswherethesubgradesoilisextremelyweak.Itmayalsobeused,intheinterestsofeconomy,inlocationswheresuitablesubbasematerialarecheapthanbasematerialsofhigherquality.

Thesubgradeisthefoundationlayer,thestructurethatmusteventuallysupportalltheloadswhichcomeontothepavement.Insomecasesthislayerwillsimplybethenaturalearthsurface.Inotherormoreusualinstancesitwillbecompactedsoilexistinginacutsectionortheupperlayerofanembankmentsection.Inthefundamentalconceptoftheactionofflexiblepavement,thecombinedthicknessofsubbase（ifused）,base,andwearingsurfacemustbegreatenoughtoreducethestressesoccuringinthesubgradetovaluesthatarenotsufficientlygreattocauseexcessivedistortionordisplacementofthesubgradesoillayer.

Theprinciplefactorsenteringintotheproblemofthethicknessdesignofflexiblepavementare:

（1）Trafficloading.

（2）Climateorenvironment.

（3）Materialcharacteristics.

Anumberofotherelementsmustalsobeconsideredinordertoarriveatafinalthicknessdesign.Thisincludecost,construction,maintenance,andesignperiod.Thus,thestudentsshouldrealizethatthedesignprocessiscomplex,anditishighlyunlikelythatanyextremelysimplemethodofapproachwillproveentirelysuccessfulunderallconditions.

Protectionofthesubgradefromtheloadingimposedbytrafficisoneoftheprimariyfunctionsofapavementstructure.Thedesignermustprivideapavementthatcanwithstandalargenumberofrepeatedapplicationsofvariable-magnitudeloading.

Themagnitudeofmaximumloadingiscommonlycontrolledbylegalloadlimits.Trafficsurveysandloadometerstudiesareoftenusedtoestablishtherelativemagnitudeandoccurrenceofthevariousloadingtowhichapavementissubjected.Predictionorestimationofthetotaltrafficthatwilluseapavementduringitsdesignifeisaverydifficultbutobviouslyimportanttask.

Theclimateorenvironmentinwhichaflexiblepavementistobeestablishedhasanimportantinfluenceonthebehaviorandperformanceofthevariousinthepavementandsubgrade.Probabllythetwoclimatefactorsofmajorsignificancearetemperatureandmoisture.

Themagnitudeoftemperatureanditsfluctuationsaffectthepropertiesofcertainmaterials.Forexample,hightemperaturescauseasphalticconcretetolosestabilitywhereasatlowtemperaturesasphalticconcretebecomesveryhardandstiff.Lowtemperatureandtemperaturefluctuationsarealsoassociatedwithfrostheaveandfreeze-thawdamage.

Granularmaterials,ifnotproperlygraded,canexperiencefrostheave.Likewise,thesubgradecanexhibitextensivelossinstrengthifitbecomesfrozen.Certainstabilizedmaterials（lime,cement,andlime-flyashtreated）cansuffersubstantialdamageifalargenumberoffreeze-thawcyclesoccurinthematerial.

Moisturealsohasanimportantinfluenceonthebehaviorandperformanceofmanymaterials.Moistureisanimportantingredientinfrost-relateddamage.Subgradesoilsandotherpavingmaterialsweakenappreciablywhensaturated,andcertainclayeysoilexhibitsubstantialmoisture-includedvolumechange.

Subgrademoistureconditionschangeisaffectingroadstructuralstrength,stiffnessandstabilityoftheimportantfactors.Subgrademoistureinfluencehasthefollowingmainfactors:

atmosphericprecipitationandevaporation,infiltrationofsurfacewater,groundwaterimpact,temperaturechangescausedbyhumidity.

Cyclicalatmospherictemperaturechangesthroughouttheyear,dayandnighttemperaturesforeachdayacertainextentcyclicalchanges.Surfacedirectlyexposedtotheair,andexperiencingtheimpactofthesechanges,inparticularsurfacematerialmostaffected.Roadsurfacetemperaturechangewiththeweathertemperatureisroughlysynchronized.Surfacelayertemperatureatdifferentdepthswithinthesamegenerationasthecyclicalchangesinatmospherictemperature,butthemagnitudeofchangeincreaseswiththedepthgraduallydecreased.

Oneoffrostdamageisfrozen,itnotonlyaffectsthenormalrunningofvehicles,andsometimesthedestructionofthepavementstructure.Producefrostheavefortworeasons:

First,aswaterisfrozen,thevolumewillincreaseby9%;secondisduetotheweakfoundationsoiltofreezetheareawithwatermovementresults.Subgradefrostheavingcausedbythreefactors:

thesensitivityoffrozensoilsubgrade;temperaturedecreasedslowly;groundwatersupplyofwatertokeepthefrozenzone.

Theadventofspring,begantomeltthefrozenroadbed,willlosetheirbearingcapacityofsoil,leadingtoroaddamage,aphenomenonknownasthespringmeltboil,boilandmainlyduetothemeltingprocessistopdown,whentheembankmenttopsoilbeginstomelt,thewatercannotbeexcluded,sothesoilhasbeensaturatedmelting.Ifbythistimealargenumberofheavyvehicles,roadstructurewouldbeseriouslydamaged.

Oftheroadisasticky,elastic-plasticmaterialsandthecombinationofmineralaggregateparticlesconsistingofroads,includingtheadditionofcementconcreteasasurfacelayerandthesurfacestructureofavarietyofothergrass-rootslevel.Flexiblepavementdesignincludingpavementlayercombinationofdesign,structuralcalculationandtheroadpavementmaterialmixdesign.Thischapterelaboratesthefollowingaspects:

elasticlayeredsystemtheory,thepavementlayercombinationofdesignprinciples,roaddesignstandardsandparameters,calculationofpavementthicknessandthebendingstresscheck.

Inreality,theroadbasematerialandthesoilisnotinanycasehaveelasticproperties.Non-linearelastic-viscous-plastictheory,undercertainconditionsmoreaccuratelydescribethestressstateoftheroad,buttakingintoaccounttheroleofthetransientdrivingwheelsinthepavementstructure,thestresswassmall,soyoucanroadaseachlayerisanidealelasticbody,multi-layerlinearelastictheorytoapplicationtodesigncalculations.Multi-layerlinearelastictheorymustbeusedthefollowingbasicassumptions:

1.Layersofmaterialarecontinuous,homogeneous,isotropicandtoobeyHooke'slaw,andthedisplacementanddeformationissmall;

2.Thenextlevel（soilbasis）inthehorizontaldirectionandverticaldirectiondowntoinfinity,Theelasticlayerisaboveallhaveacertainthickness,butthehorizontaldirectionisinfinite;

3.