专业英语Word文件下载.docx

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Hotrolledasphalt（HRA）（热压沥青混凝土）isagapgraded（间断级配）materialwithlesscoarseaggregate（粗集料）.Infactitisessentiallyabitumen/fineaggregate（细集料）/filler（填料）mortar（胶浆）intowhichsomecoarseaggregateisplaced.

Themechanicalpropertiesaredominatedbythoseofthemortar.ThismaterialhasbeenextensivelyusedasthewearingcourseonmajorroadintheUK,thoughitsusehasrecentlydeclinedasnewmaterialshavebeenintroduced.

Itprovidesadurable（耐久的、耐用的）layerwithgoodresistancetocrackingandonewhichisrelativelyeasytocompact（压实）.Thecoarseaggregatecontentislow（typically30%）whichresultsinthecompactedmixturehavingasmoothsurface.Accordingly（因此）,theskidresistanceisinadequateandprecoated（预浇）chippings（石屑）arerolledintothesurfaceatthetimeoflayingtocorrectthisdeficiency（不足）.

InScotland,HRAwearingcourseremainsthepreferredwearingcourseontrunkroads（干线道路）includingmotorway（高速公路、汽车专用公路）but，since1999thinsurfacingshavebeenthepreferredoptioninEnglandandWales.Since1999inNorthernIreland,HRAwearingcourseandthinsurfacingsarethepreferredpermittedoptions.

Porousasphalt（PA）isauniformlygraded（单一级配）materialwhichisdesignedtoprovidelargeairvoids（空隙率）sothatwatercandraintotheverges（路肩、边缘）withinthelayerthickness.Ifthewearingcourseistobeeffective,thebasecourse（基层）belowmustbewaterproof（防水的）andthePAmusthavetheabilitytoretainitsopentextured（构造、纹理）propertieswithtime.

Thickbinderfilms（吸附沥青膜）arerequiredtoresistwaterdamage（水损害）andageing（老化）ofthebinder.Inuse,thismaterialminimizesvehiclespray（水雾）,providesaquietrideandlowerrollingresistancetotrafficthandensemixtures（密级配混合料）.

Itisoftenspecified（指定）forenvironmentalreasonsbutstonemasticasphalt（SMA）（沥青玛蹄脂碎石）andspeciallythinsurfacingsaregenerallyfavouredincurrentUKpractice.

TherehavebeenhighprofileinstanceswhereaPAwearingcoursehasfailedearlyinitslife.TheHighwaysAgency（公路局）doesnotrecommendtheuseofaPAattrafficlevelsabove6000commercialvehicles（载重车）perday.

Asphalticconcrete（沥青混凝土）anddensebitumenmacadam（DBM）（密级配沥青碎石）arecontinuouslygradedmixtures（连续级配混合料）similarinprincipletotheDBMsusedinroadbases（基层）andbasecoursesbutwithsmallermaximumparticlesizes（最大粒径）.

Asphalticconcretetendstohaveaslightly（稍微）densergradingandisusedforroadsurfacesthroughouttheworldwiththeexceptingoftheUK.

ItismoredifficulttomeetUKskidresistanceStandards（抗滑标准）withDBMsthanHRA,SMAorPA.ThisproblemcanberesolvesbyprovidingaseparatesurfacetreatmentbutdoingsogenerallymakesDBMeconomicallyunattractive.

Stonemasticasphalt（SMA）materialwaspioneered（开辟、开路）inGermanyandScandinaviaandisnowwidelyusedintheUK.SMAhasacoarse,aggregrateskeleton（碎石骨架）,likePA,butthevoidsarefilledwithafineaggregate/filler（填料）/bitumenmortar.

®

Inmixturesusingpenetrationgradebitumen（石油沥青）,fibres（纤维）areaddedtohold（吸收、吸附）thebitumenwithinthemixture（toprevent“binderdrainage”）.

Bitumen

oilbitumen（earthoil）

naturalbitumen

Tar

Whereapolymermodifiedbitumen（聚合物改性沥青）isused,thereisgenerallynoneedforfibres.SMAisagap-gradedmaterialwithgoodresistancetoruttingandhighdurability（耐久性）.

modifiedbitumen

SBS

SBR

PE\EVA

ItdiffersfromHRAinthatthemortarisdesignedtojustfillthevoidsinthecoarseaggregatewhereas,inHRA,coarseaggregateisintroducedintothemortaranddoesnotprovideacontinousstonematrix（矿质骨架）.

ThehigherstonecontentHRAs,however,arerathersimilartoSMAbutarenotwideusedaswearingcoursesintheUK,beingpreferredforroadbaseandbasecourseconstruction.

Avarietyofthinandwhatwerecalledultra（超的、极端的）thinsurfacings（nowadays,thetendencyistousetheterm‘thinsurfacings’forboththinandultrathinsurfacings）havebeenintroducedinrecentyears,principallyasaresultofdevelopmentworkconcentrated（集中）inFrance.

Thesematerialsvaryintheirdetailedconstituents（成分、要素、组成部分）butusuallyhaveanaggregategradingsimilartoSMAandoftenincorporate（联合、结合、加入）apolymermodifiedbitumen.

Theymaybeusedoverahighstiffnessroadbaseandbasecourseorusedforresurfacing（翻修路面）ofexistingpavements.Forheavydutypavements（i.ethosedesignedtohaveausefullifeoffortyyears）,themaintenancephilosophy（哲学、哲理）isoneofminimumlaneoccupancy（占用）,whichonlyallowstimeforreplacement（替换）ofthewearingcoursetothese‘longlife’pavementstructures.Thenewgenerationofthinsurfacingsallowsthistobeconvenientlyachieved.

Thevariousgeneric（种类的）mixturetypesdescribedabovecanbecomparedwithrespecttotheirmechanicalpropertiesanddurabilitycharacteristicsbyreference（参考）toFig.12.1.Thisshows,inprinciple,howlowstonecontentHRA,asphalticconcrete,SMAandPAmixturesmobilizeresistance（流动阻力）toloadingbytraffic

Asphalticconcrete（Fig.12.1a））presentssomethingofacompromise（和解、折衷方案）whenwelldesigned,sincethedenseaggregategradingcanoffergoodresistancetotheshearstresses（剪切应力）whichcauserutting,whileanadequatebindercontentwillprovidereasonableresistancetothetensilestresses（拉应力）

whichcausecracking.

Ingeneral,theroleoftheaggregatedominates.DBMstendtohavelessdensegradingsandpropertieswhich,therefore,tendtowardsgoodruttingresistanceandawayfromgoodcrackresistance.

HRA（Fig.12.1b））offersparticularlygoodresistancetocrackingthroughthebinderrichmortarbetweenthecoarseaggregateparticles.Thisalsoprovidesgooddurabilitybutthelackofcoarseaggregatecontentinhibits（防止、制止）resistancetorutting.

SMAandPAareshowninthesamediagram（Fig.c））toemphasisthedominantrolethecoarseaggregate.Inbothcase,wellcoatedstoneisused.InPA,thevoidspaceremainsavailablefordrainageofwater,whilstinSMA,thespaceisoccupiedbyafineaggregate/filler/bitumen/fibremortar.

Bothmaterialsoffergoodruttingresistancethroughthecoarseaggregatecontent.ThetensilestrengthofPAislowwhilstthatofSMAisprobablyadequatebutlittlemechanicaltestingdatahavebeenreportedtodate.

13

Provisionofadequatedrainage（排水）isimportantfactorinthelocation（定位）andgeometric（几何学的、几何图形的）designofroadandairports.Drainagefacilities（排水设施）onanyhighway,streetandairportshouldadequatelyprovidefortheflowofwaterawayfromthesurfaceofthepavementtoproperlydesignedchannels.

Inadequatedrainagewilleventually（最后、终于）resultinseriousdamagetothestructure.

Inaddition,trafficmaybeslowedbyaccumulatedwater（积水）onthepavement,andaccidentsmayoccurasaresultofhydroplaning（水滑现象）andlossofvisibilityfromsplash（喷溅）andspray（喷洒、喷雾）.

Theimportanceofadequatedrainageisrecognizedintheamountofhighwayconstructiondollarsallocated（分配、分派）todrainagefacilities.

About25percentofhighwayconstructiondollarsarespentforerosion（冲刷、侵蚀）controlanddrainagestructures,suchasculverts（涵洞）,bridges,channels,andditches（（明）沟、渠）.

HighwayDrainageStructures（公路排水结构物）

Oneofthemainconcernsofthehighwayengineeristoprovideanadequatesizestructure,suchthatthewaterwayopening（过水孔径）issufficientlylargetodischarge（放、排出）theexpectedflowofwater.

Inadequatelysizedstructurescanresultinwaterimpounding（集水、蓄水）,whichmayleadtofailureoftheadjacent（邻近的）sectionsofthehighwayduetoembankments（路堤）beingsubmerged（浸没、浸入水中）inwaterforlongperiods.

Thetwogeneralcategoriesofdrainagestructuresaremajorandminor.Majorstructures（大型结构物）arethosewithclearspans（净跨（径））greaterthan20feet,whereasminorstructuresarethosewithclearspansof20feetorless.

Majorstructuresareusuallylargebridges,althoughmultiple-spanculverts（多孔涵洞）mayalsobeincludedinthisclass.Minorstructuresincludesmallbridgesandculverts.

Emphasisisplacedonselectingthespanandverticalclearance（净空）requirementsformajorstructures.Thebridgedeck（桥面）shouldbelocatedabovethehighwatermark（高水位线）.Theclearanceabovethehighwatermarkdependsonwhetherthewaterwayisnavigable（可通行的、可通航的）.

Ifthewaterwayisnavigable,theclearanceabovethehighwatermarkshouldallowthelargestshipusingthechanneltopassunderneath（在…下面）thebridgewithoutcollidingwith（碰撞）thebridgedeck.

Theclearanceheight（净空高度）,type,andspacingofpiers（桥墩）alsodependontheprobabilityoficejams（冰块拥塞）andtheextent（程度）towhichfloatinglogs（漂浮的圆木）anddebris（垃圾）appearonthewaterwayduringhighwater.

Anexaminationofthebanks（堤（岸））oneithersideofthewaterwaywillindicatethelocationofthehighwatermark,sincethisisusuallyassociatedwithsignsoferosion（冲刷、侵蚀）anddebrisdeposits（沉淀物、沉积物）.Localresidents,whohavelivednearandobservedthewaterwayduringfloodstages（洪水期间）overanumberofyears,canalsogivereliable（可靠的）informationonthelocationofthehighwatermark.Streamgauges（水文站）thathavebeeninstalledinthewaterwayformanyyearscanalsoprovidedatathatcanbeusedtolocatethehighwatermark.

Minorstructures,consistingofshort-spanbridgesandculverts,arethepredominant（占优势的、主要的）typeofdrainagestructuresonhighways.