道路工程(路橋)畢業(yè)設計外文文獻翻譯

./外文文獻翻譯原文：AsphaltMixtures-Applications,TheoryandPrinciples1.ApplicationsAsphaltmaterialsfindwideusageintheconstructionindustry.Theuseofasphaltasacementingagentinpavementsisthemostcommonofitsapplications,however,andtheonethatwillbeconsideredhere.Asphaltproductsareusedtoproduceflexiblepavementsforhighwaysandairports.Theterm"flexible"isusedtodistinguishthesepavementsfromthosemadewithPortlandcement,whichareclassifiedasrigidpavements,thatis,havingbeamstrength.Thisdistinctionisimportantbecauseitprovidestheykeytothedesignapproachwhichmustbeusedforsuccessfulflexiblepavementstructures.Theflexiblepavementclassificationmaybefurtherbrokendownintohighandlowtypes,thetypeusuallydependingonwhetherasolidorliquidasphaltproductisused.Thelowtypesofpavementaremadewiththecutback,oremulsion,liquidproductsandareverywidelyusedthroughoutthiscountry.Descriptiveterminologyhasbeendevelopedinvarioussectionsofthecountrytotheextentthatonepavementtypemayhaveseveralnames.However,thegeneralprocessfollowedinconstructionissimilarformostlow-typepavementsandcanbedescribedasoneinwhichtheaggregateandtheasphaltproductareusuallyappliedtotheroadbedseparatelyandtheremixedorallowedtomix,formingthepavement.Thehightypeofasphaltpavementsismadewithasphaltcementsofsomeselectedpenetrationgrade.Fig.?1Amodernasphaltconcretehighway.Shoulderstripingisusedasasafelyfeature.Fig.?2AsphaltconcreteattheSanFranciscoInternationalTheyareusedwhenhighwheelloadsandhighvolumesoftrafficoccurandare,therefore,oftendesignedforaparticularinstallation.2.TheoryofasphaltconcretemixdesignHightypesofflexiblepavementareconstructedbycombininganasphaltcement,ofteninthepenetrationgradeof85to100,withaggregatesthatareusuallydividedintothreegroups,basedonsize.Thethreegroupsarecoarseaggregates,fineaggregates,andmineralfiller.Thesewillbediscussedindetailinlaterchapter.Eachoftheconstituentpartsmentionedhasaparticularfunctionintheasphaltmixture,andmixproportioningordesignistheprocessofensuringthatnofunctionisneglected.Beforetheseindividualfunctionsareexamined,however,thecriteriaforpavementsuccessandfailureshouldbeconsideredsothatdesignobjectivescanbeestablished.Asuccessfulflexiblepavementmusthaveseveralparticularproperties.First,itmustbestable,thatistoresistanttopermanentdisplacementunderload.Deformationofanasphaltpavementcanoccurinthreeways,twounsatisfactoryandonedesirable.Plasticdeformationofapavementfailureandwhichistobeavoidedifpossible.Compressivedeformationofthepavementresultsinadimensionalchangeinthepavement,andwiththischangecomealossofresiliencyandusuallyadegreeofroughness.Thisdeformationislessseriousthantheonejustdescribed,butit,too,leadstopavementfailure.Thedesirabletypeofdeformationisanelasticone,whichactuallyisbeneficialtoflexiblepavementsandisnecessarytotheirlonglife.Thepavementshouldbedurableandshouldofferprotectiontothesubgrade.Asphaltcementisnotimpervioustotheeffectsofweathering,andsothedesignmustminimizeweathersusceptibility.Adurablepavementthatdoesnotcrackorravelwillprobablyalsoprotecttheroadbed.Itmustberememberedthatflexiblepavementstransmitloadstothesubgradewithoutsignificantbridgingaction,andsoadryfirmbaseisabsolutelyessential.Rapidlymovingvehiclesdependonthetire-pavementfrictionfactorforcontrolandsafety.Thetextureofthepavementsurfacesmustbesuchthatanadequateskidresistanceisdevelopedorunsafeconditionsresult.Thedesignprocedureshouldbeusedtoselecttheasphaltmaterialandaggregatescombinationwhichprovidesaskidresistantroadway.Designprocedureswhichyieldpavingmixturesembodyingallthesepropertiesarenotavailable.Soundpavementsareconstructedwherematerialsandmethodsareselectedbyusingtime-testedtestsandspecificationsandengineeringjudgmentsalongwithaso-calleddesignmethod.Thefinalrequirementforanypavementisoneofeconomy.Economy,again,cannotbemeasureddirectly,sincetrueeconomyonlybeginswithconstructioncostandisnotfullydeterminableuntilthefullusefullifeofthepavementhasbeenrecorded.If,however,therequirementsforastable,durable,andsafepavementaremetwithareasonablesafetyfactor,thenthebestinterestsofeconomyhaveprobablybeenservedaswell.Withtheserequirementsinmind,thefunctionsoftheconstituentpartscanbeexaminedwithconsiderationgivetohoweachpartcontributestonow-establishedobjectivesorrequirements.Thefunctionsoftheaggregatesistocarrytheloadimposedonthepavement,andthisisaccomplishedbyfrictionalresistanceandinterlockingbetweentheindividualpiecesofaggregates.Thecarryingcapacityoftheasphaltpavementis,then,relatedtothesurfacetexture<particularlythatofthefineaggregate>andthedensity,or"compactness,",oftheaggregates.Surfacetexturevarieswithdifferentaggregates,andwhilearoughsurfacetextureisdesired,thismaynotbeavailableinsomelocalities.Densemixturesareobtainedbyusingaggregatesthatareeithernaturallyorartificially"wellgraded".Thismeansthatthefineaggregateservestofillthevoidsinthecoarseraggregates.Inadditiontoaffectingdensityandthereforestrengthcharacteristics,thegradingalsoinfluencesworkability.Whenanexcessofcoarseaggregateisused,themixbecomesharshandhardtowork.Whenanexcessofmineralfillerisused,themixesbecomegummyanddifficulttomanage.Theasphaltcementintheflexiblepavementisusedtobindtheaggregateparticlestogetherandtowaterproofthepavements.Obtainingtheproperasphaltcontentisextremelyimportantandbearsasignificantinfluenceonalltheitemsmarkingasuccessfulpavement.Achiefobjectiveofallthedesignmethodswhichhavebeendevelopedistoarriveatthebestasphaltcontentforaparticularcombinationofaggregates.3.MixdesignprinciplesCertainfundamentalprinciplesunderliethedesignproceduresthathavebeendeveloped.Beforetheseprocedurescanbeproperlystudiedorapplied,someconsiderationoftheseprinciplesisnecessary.Asphaltpavementsarecomposedofaggregates,asphaltcement,andvoids.Consideringtheaggregatealone,allthespacebetweenparticlesisvoidspace.Thevolumeofaggregatevoidsdependsongradingandcanvarywidely.Whentheasphaltcementisadded,aportionoftheseaggregatevoidsisfilledandafinalair-voidvolumeisretained.Theretentionofthisair-voidvolumeisveryimportanttothecharacteristicsofthemixture.Thetermair-voidvolumeisused,sincethesevoidsareweightlessandareusuallyexpressedasapercentageofthetotalvolumeofthecompactedmixture.Anasphaltpavementcarriestheappliedloadbyparticlefrictionandinterlock.Iftheparticlesarepushedapartforanyreason,thenthepavementstabilityisdestroyed.Thisfactorindicatesthatcertainlynomoreasphaltshouldbeaddedthantheaggregatevoidscanreadilyhold.However,asphaltcementissusceptibletovolumechangeandthepavementissubjecttofurthercompactionunderuse.Ifthepavementhasnoairvoidswhenplaced,orifitlosesthemundertraffic,thentheexpandingasphaltwilloverflowinaconditionknownasbleeding.Thelossofasphaltcementthroughbleedingweakensthepavementandalsoreducessurfacefriction,makingtheroadwayhazardous.Fig.?3Crosssectionofanasphaltconcretepavementshowingtheaggregateframeworkboundtogetherbyasphaltcement.Theneedforaminimumair-voidvolume<usually2or3percent>hasbeenestablished.Inaddition,amaximumair-voidvolumeof5to7percentshouldnotbeexceed.Anexcessofairvoidspromotesravelingofthepavementandalsopermitswatertoenterandspeedupthedeterioratingprocesses.Also,inthepresenceofexcessairtheasphaltcementhardensandageswithanaccompanyinglossofdurabilityandresiliency.Theair-voidvolumeofthemixisdeterminedbythedegreeofcompactionaswellasbytheasphaltcontent.Foragivenasphaltcontent,alightlycompactedmixwillhavealargevoidsvolumeandalowerdensityandagreaterstrengthwillresult.Inthelaboratory,thecompactioniscontrolledbyusingaspecifiedhammerandregulatingthenumberofblowsandtheenergyperblow.Inthefield,thecompactionandtheairvoidsaremoredifficulttocontrolandtestsmustbemadenospecimenstakenfromthecompactedpavementtocheekonthedegreeofcompactionbeingobtained.Trafficfurthercompactthepavement,andallowancemustbemadeforthisinthedesign.Asystematiccheckingofthepavementoveranextendedperiodisneededtogivenfactualinformationforaparticularmix.Achangeindensityofseveralpercentisnotunusual,however.Asphaltcontenthasbeendiscussedinconnectionwithvariousfacetsoftheixdesignproblem.Itisaveryimportantfactorinthemixdesignandhasabearinganallthecharacteristicsldasuccessfulpavement:stability,skidresistance,durability,andeconomy.Ashasbeenmentioned,thevariousdesignproceduresareintendedtoprovideameansforselectingtheasphaltcontent.Thesetestswillbeconsideredindetailinafuturechapter,buttherelationshipbetweenasphaltcontentandthemeasurablepropertiesofstability,unitweight,andairvoidswillbediscussedhere.Fig.4Variationsinstability,unitweight,andair-voidcontentwithasphaltcementcontent.Ifthegradationandtypeofaggregate,thedegreeofcompaction,andthetypeofasphaltcementarecontrolled,thenthestrengthvariesinapredictablemanner.Thestrengthwillincreaseuptosomeoptimumasphaltcontentandthendecreasewithfurtheradditions.Thepatternofstrengthvariationwillbedifferentwhentheothermixfactorsarechanged,andsoonlyatypicalpatterncanbepredictedpriortoactualtesting.Unitweightvariesinthesamemannerasstrengthwhenallothervariablearecontrolled.Itwillreachsomepeakvalueatanasphaltcontentnearthatdeterminedfromthestrengthcurveandthenfalloffwithfurtheradditions.Asalreadymentioned,theair-voidvolumewillvarywithasphaltcontent.However,themannerofvariationisdifferentinthatincreasedasphaltcontentwilldecreaseair-voidvolumetosomeminimumvaluewhichisapproachedasymptotically.Withstillgreateradditionsofasphaltmaterialtheparticlesofaggregateareonlypushedapartandnochangeoccursinair-voidvolume.Insummary,certainprinciplesinvolvingaggregategradation,air-voidvolume,asphaltcontent,andcompactionmistbeunderstoodbeforeproceedingtoactualmixdesign.Theproperdesignbasedontheseprincipleswillresultinsoundpavements.Iftheseprinciplesareoverlooked,thepavementmayfailbyoneormoreoftherecognizedmodesoffailure:shoving,rutting,corrugating,becomingslickwhenthemaxistoo‘rich’;raveling,cracking,havinglowdurabilitywhenthemixistoo‘lean’.Itshouldbeagainemphasizedthatthestrengthofflexibleis,moreaccurately,astabilityanddoesnotindicateanyabilitytobridgeweakpointsinthesubgradebybeamstrength.Noasphaltmixturecanbesuccessfulunlessitrestsontopofaproperlydesignedandconstructedbasestructure.Thisfact,thatthesurfaceisnobetterthanthebase,mustbecontinuallyinthemindsofthoseconcernedwithanyaspectofflexiblepavementwork.譯文：瀝青混合料的應用、理論和原則1、應用瀝青材料如今在建筑行業(yè)廣泛使用。瀝青最常見的應用是作為的瀝青路面的粘結劑使用。然而,這一點必須在這里予以介紹。瀝青產品常用于生產公路和機場柔性路面。所謂"柔性"是用來區(qū)分與硅酸鹽水泥制成的路面,它被列為剛性路面,也就是這些路面具有剛性強度。這個區(qū)別很重要,因為它提出了成功進行柔性路面結構設計的方法的關鍵。柔性路面的分類可進一步細分為高、低的類別,分類通常取決于是否有使用固體或液體瀝青產品。低類型路面結構類型通過減少瀝青用量或使用乳化劑、液體瀝青,是非常廣泛的應用在全國圍。在全國的圍各地區(qū)已開發(fā)各自的描述性術語,一個路面類型可能有好幾個名字。但是,一般對大多數(shù)低型路面其施工方法確是相似,可描述為瀝青產品通常單獨或其混合結構應用于行車道,形成路面。高級瀝青路面用經過選擇的具有好的滲透性的瀝青混凝土制成。圖1現(xiàn)代瀝青混凝土公路路肩設置路標線具有安全地特點圖2舊金山國際機場瀝青混凝土跑道它們被用于重荷載和大交通量道路,因此,人們會進行特殊的結構設計。2、瀝青混凝土設計原理高等級柔性路面是用瀝青混凝土建造而成,通常根據(jù)集料的85%-100%通過率將其分為三種類型。這三種分別為粗集料、細集料和礦粉。這些將在后面的章節(jié)中進行詳細討論。瀝青混合料的每一個組成部分都有特定的功能,混合料配合比設計是確保沒有功能被忽略的過程。然而,在這些個別功能檢查之前,對于路面的成功和失敗的標準應該考慮,這樣路面的設計目標才能確定。一個成功的柔性路面必須有幾個特定的屬性。首先,它必須是穩(wěn)定的,即抵抗負荷下的永久位移。瀝青路面變形的可能發(fā)生在三種方式,二個是不理想的形變,一個是可以接受的。塑性變形對路面來說是要盡量避免的失敗。路面的壓縮變形導致的路面鋪裝的尺寸變化,這種變化將引起路面彈性和粗糙度的損失。這種變形沒有剛剛描述的那種那么嚴重,但它也同樣導致路面破壞。理想類型的變形是一種彈性變形,這實際上有利于柔性路面,并對于其長壽命是十分必要的。路面應該耐用并能夠保護路基。瀝青混凝土是受環(huán)境的影響的,因此設計必須降低對氣候敏感性。一個耐用的路面要不開裂或擁包才能保護路基。我們必須記住,柔性路面將荷載直接傳至路基,所以堅實的基礎是絕對必要的?？焖僖苿拥能囕v依靠的輪胎路面摩擦力實現(xiàn)控制和保證安全。路面表面紋理必須保證足夠的防滑性否則將產生不安全的后果。設計過程通過瀝青材料的選擇和集料的組合設計提供了防滑路面。設計程序放棄鋪面結合料所有這些表面特性都無法使用。合理的路面建造所需的材料和方法是經過使用時間考驗和規(guī)和工程判斷和在一起所稱的設計方法選定。對于任何路面最后一個要經濟性。經濟性不能一開始就確定,準確的經濟是從開始建設直到路面整個壽命期的成本。然而,如果對于路面穩(wěn)定,耐久,安全性的要求都達到一個合理的安全系數(shù),那么對經濟的最佳利益或許已經實現(xiàn)。考慮到路面的這些要求,可通過檢查各組成部分的功能如何有助于現(xiàn)在已經確定的目標或要求。瀝青混凝土功能是承擔路面上施加的負荷,這是由混合料各材料之間相互咬合和摩擦阻力實現(xiàn)。也就是瀝青路面的承載能力與路面的表面紋理〔尤其是細集料和密度或者混合料的"密實度"相關,表面結構隨集料的不同而不同,雖然理想的表面具有粗糙紋理,但在有些情況下卻不能實現(xiàn)。密級配混合物通過使用自然或人為的連續(xù)級配集料得到。這意味著細骨料的存在填補了粗骨料的空隙。這除了影響混合料的密度和強度特性之外,也影響施工性能。當粗骨料使用過量時,混合料將變得堅硬而且難以施工；當?shù)V物填料使用過多時,混合料將變得較軟,影響使用性能。柔性路面中的瀝青膠結材料用于將集料粘結在一起并充當防水材料。選取適當?shù)臑r青含量是非常重要的,它對于成功的路面在項目的整個評分過程中具有重要的影響。設計的首要目標是對于特定的集料組合確定瀝青的最佳