道路工程(路橋)畢業(yè)設(shè)計(jì)外文文獻(xiàn)翻譯

./外文文獻(xiàn)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(yīng)用、理論和原則1、應(yīng)用瀝青材料如今在建筑行業(yè)廣泛使用。瀝青最常見的應(yīng)用是作為的瀝青路面的粘結(jié)劑使用。然而,這一點(diǎn)必須在這里予以介紹。瀝青產(chǎn)品常用于生產(chǎn)公路和機(jī)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(qiáng)度。這個(gè)區(qū)別很重要,因?yàn)樗岢隽顺晒M(jìn)行柔性路面結(jié)構(gòu)設(shè)計(jì)的方法的關(guān)鍵。柔性路面的分類可進(jìn)一步細(xì)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(chǎn)品。低類型路面結(jié)構(gòu)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(yīng)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(shù)語,一個(gè)路面類型可能有好幾個(gè)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(chǎn)品通常單獨(dú)或其混合結(jié)構(gòu)應(yīng)用于行車道,形成路面。高級瀝青路面用經(jīng)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(shè)置路標(biāo)線具有安全地特點(diǎn)圖2舊金山國際機(jī)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(jìn)行特殊的結(jié)構(gòu)設(shè)計(jì)。2、瀝青混凝土設(shè)計(jì)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(xì)集料和礦粉。這些將在后面的章節(jié)中進(jìn)行詳細(xì)討論。瀝青混合料的每一個(gè)組成部分都有特定的功能,混合料配合比設(shè)計(jì)是確保沒有功能被忽略的過程。然而,在這些個(gè)別功能檢查之前,對于路面的成功和失敗的標(biāo)準(zhǔn)應(yīng)該考慮,這樣路面的設(shè)計(jì)目標(biāo)才能確定。一個(gè)成功的柔性路面必須有幾個(gè)特定的屬性。首先,它必須是穩(wěn)定的,即抵抗負(fù)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(gè)是不理想的形變,一個(gè)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(dǎo)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(yán)重,但它也同樣導(dǎo)致路面破壞。理想類型的變形是一種彈性變形,這實(shí)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(yīng)該耐用并能夠保護(hù)路基。瀝青混凝土是受環(huán)境的影響的,因此設(shè)計(jì)必須降低對氣候敏感性。一個(gè)耐用的路面要不開裂或擁包才能保護(hù)路基。我們必須記住,柔性路面將荷載直接傳至路基,所以堅(jiān)實(shí)的基礎(chǔ)是絕對必要的。快速移動的車輛依靠的輪胎路面摩擦力實(shí)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(chǎn)生不安全的后果。設(shè)計(jì)過程通過瀝青材料的選擇和集料的組合設(shè)計(jì)提供了防滑路面。設(shè)計(jì)程序放棄鋪面結(jié)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(jīng)過使用時(shí)間考驗(yàn)和規(guī)和工程判斷和在一起所稱的設(shè)計(jì)方法選定。對于任何路面最后一個(gè)要經(jīng)濟(jì)性。經(jīng)濟(jì)性不能一開始就確定,準(zhǔn)確的經(jīng)濟(jì)是從開始建設(shè)直到路面整個(gè)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(dá)到一個(gè)合理的安全系數(shù),那么對經(jīng)濟(jì)的最佳利益或許已經(jīng)實(shí)現(xiàn)?？紤]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(jīng)確定的目標(biāo)或要求。瀝青混凝土功能是承擔(dān)路面上施加的負(fù)荷,這是由混合料各材料之間相互咬合和摩擦阻力實(shí)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(xì)集料和密度或者混合料的"密實(shí)度"相關(guān),表面結(jié)構(gòu)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(shí)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(xì)骨料的存在填補(bǔ)了粗骨料的空隙。這除了影響混合料的密度和強(qiáng)度特性之外,也影響施工性能。當(dāng)粗骨料使用過量時(shí),混合料將變得堅(jiān)硬而且難以施工；當(dāng)?shù)V物填料使用過多時(shí),混合料將變得較軟,影響使用性能。柔性路面中的瀝青膠結(jié)材料用于將集料粘結(jié)在一起并充當(dāng)防水材料。選取適當(dāng)?shù)臑r青含量是非常重要的,它對于成功的路面在項(xiàng)目的整個(gè)評分過程中具有重要的影響。設(shè)計(jì)的首要目標(biāo)是對于特定的集料組合確定瀝青的最佳