公路工程课件

Lesson27HIGHWAYENGINEERINGTransportationhasalwaysbeenoneofthemostimportantaspectsofcivilengineering.OneofthegreatestaccomplishmentsofRomanengineerswasthehighwaysystemthatmaderapidcommunicationpossiblebetweenRomeandtheprovincesoftheempire.Modernhighwaysarebuiltaccordingtotheprincipleslaiddownintheeighteenthandearlynineteenthcenturies.Generallyspeaking,alignment,subgrade,andpavementarethemostbasicthreepartsofthemodernhighways.交通一直是土木工程中最重要的方面之一。一位罗马工程师的最伟大的成就是公路体系，其使快速通讯成为可能。现代公路的修建是根据十八和十九世纪初所定下的原则。一般而言，线性，路基，路面是现代公路的最基本的三个部分。

Introductionaccomplishment成就alignment线性subgrade路基pavemen路面Thealignmentofaroadincludeshorizontalalignmentandverticalalignment.Thehorizontalalignmentofaroadisshownontheplanviewandisaseriesofstraightlinescalledtangentsconnectedbycircularcurves.Inmodernpracticeitiscommontointerposetransitionorspiralcurvesbetweentangentsandcircularcurves.Sotheelementsofthehorizontalalignmentaretangent,circularcurve,andtransitioncurve,asshowninfollowingFig.27-1.公路线形包括平面线形和纵断面线形。道路的平面线形显示在平面图和一系列的直线称为圆曲线连接切线。目前在实际操作中，一般在切线和圆曲线之间插入缓和曲线或螺旋曲线。平面线形的组成是切线（直），圆曲线和过渡曲线，如图中下面的图27-1。1.Alignment（线形）horizontalalignment平面线形verticalalignment纵断面线形tangent切线circularcurve圆曲线CurvelineStraightlineTheverticalalignmentofaroadisshownonthecutawayview.Theelementsoftheverticalalignmentaretangents,verticalcurves.Usuallytherearetwotypeofverticalcurve:convexverticalcurveandconcaveverticalcurve,asshowninfollowingFig.27-2.道路的纵断面线形显示在剖视图。纵断面线形的组成是切线，竖曲线。通常有两种类型的竖曲线：垂直凸竖曲线和凹竖曲线，如图以下所示27-2。cutaway剖面convex凸的concave凹的Long,flatcurvesarepreferableatalltimes,astheyarepleasinginappearanceanddecreasepossibilityoffutureobsolescence.Long,flatcurvesshouldbeusedforsmallchangesindirection,asshortcurvesappearas'kink'.Alsohorizontalandverticalalignmentmustbeconsideredtogether,notseparately.Forexample,asharphorizontalcurvebeginningnearacrestcancreateaseriousaccidenthazard.在任何时候都长且平坦的曲线都是优选，因为它们在外观上令人愉悦并能减少将来报废的可能性。长，平面曲线应该用于在方向上的微小变化，如短的曲线显示为“扭结”。同时平面线形和纵断面线形必须一起考虑，而不是分开。例如，一个锐的平曲线的开始接近高峰时可能会产生严重事故的危险。obsolescence报废crest高峰Avehicletravelinginacurvedpathissubjecttocentrifugalforce.Thisisbalancedbyanequalandoppositeforcedevelopedthroughsuperelevationandsidefriction.Fromahighwaydesignstandpoint,bothsuperelevationandsidefrictioncannotexceedcertainmaximums,andthesecontrolsplacelimitsonthesharpnessofcurvesthatcanbeusedwithadesignspeed.车辆在弯曲道路行驶受到离心力。这个平衡通过大小相等方向相反的超高和侧向摩擦力来达到。从公路设计的观点来讲，超高和侧向摩擦力都不能超过某个最大值，这些控制值设置了曲线锐度限值，曲线锐度限值可以与设计速度建立联系。vehicle车辆centrifugalforce离心力superelevation超高sidefriction侧向摩擦力Whenroadsintersectorarailroadspansacrossaroad,theroadintersectionsareneeded.Theintersectioncanbeat-gradeintersectionandgrade-separatedjunction.Thefreewaysonlyadoptthelatterintersection.Thetypicalat-gradecrossingsarecrossroads,Tintersection,androtaryintersection,asshowninfollowingFig.27-3.当相交的道路或铁路横跨道路时，需要设置道路交叉口。交叉口可以是平面交叉的和立体交叉。该高速公路仅采用后者的交叉口。典型的平面交叉口的十字路口，T形交叉，及环形交叉，如图下所示27-3。intersect交叉junction连接rotary环形高速公路普通公路与高速公路的转弯线形的比较Whenroadsintersectorarailroadspansacrossaroad,theroadintersectionsareneeded.Theintersectioncanbeat-gradeintersectionandgrade-separatedjunction.Thefreewaysonlyadoptthelatterintersection.Thetypicalat-gradecrossingsarecrossroads,Tintersection,androtaryintersection,asshowninfollowingFig.27-3.当相交的道路或铁路横跨道路时，需要设置道路交叉口。交叉口可以是平面交叉的和立体交叉。该高速公路仅采用后者的交叉口。典型的平面交叉口的十字路口，T形交叉，及环形交叉，如图下所示27-3。intersect交叉junction连接rotary环形Thefoundationsunderpavementofhighwaysaresubgrade,sohighwaysubgrade(orbasementsoil)maybedefinedasthesupportingstructureonwhichpavementanditsspecialundercoursesrest.Thepurposeofapavementistoprovideasmoothsurfaceoverwhichvehiclesmaypassunderallclimateconditions.Becausenaturalterrainsareuneven,togetsmoothroad,cuttingandfillingareneededtochangethenaturalterrain.Subgradesareclassifiedintoembankment,cutting,andpart-cutpart-fillsubgrade,。作业：将下段英文翻译成汉语。Incutsections,thesubgradeistheoriginalsoillyingbelowthespeciallayersdesignatedasbaseandsubbasematerial.Infillsections,thesubgradeisconstructedoverthenativegroundandconsistsofimportedmaterialfromnearbyroadwaycutsorfromborrowpits.在挖方部分，路基是置于被设计为基座和底基层特殊层下方的天然土。在填方部分，路基建造于原土之上并由附近公路挖方或从取土坑中的土这类外来材料组成。Theperformanceofthepavementisaffectedbythecharacteristicsofthesubgrade.Desirablepropertiesthatthesubgradeshouldpossessincludestrength,drainage,easeofcompaction,permanencyofcompaction,andpermanencyofstrength.在路面的性能受路基特性的影响。路基的理想性能，应具有包括强度，排水，易压实性，压实的永久性和强度的永久性。drainage排水possess控制，具有Soilsengineersagreethatthepropertiesofasoilmixtureareinfluencedmorebymoisturethanbyanyothercause.Soilsthathaveamplestrengthandsupportingpowerunderonesetofmoistureconditionsmaybeentirelyunsatisfacoryifthepercentageofmoisturechanges.Onedifficultywithsoilsinhighwaysubgradesisthattheyaresubjecttosuchmoisturechanges.土力学工程师赞同湿度对土壤混合物性能的影响比其他因素大。在一个湿度条件下有足够强度与支撑能力的土体，如果湿度的百分比发生变化，土体可能完全不能令人满意。土体在公路路基中的一个困难是承受着湿度的变化。mixture混合物moisture湿度percentage

百分比Soilisahighlyvariablematerial;theinterrelationshipofsoiltexture,density,moisturecontent,andstrengtharecomplex,andbehaviorunderrepeatedloadsisdifficulttoevaluate.Becauseofthecomplexityoftheproblem,itisnotpossibletosetdownrulesthatwillbesuitableforallcase.

土壤是高度多变的材料；土壤的结构、密度、含水率及强度的内在关系是非常复杂的，在荷载重复作用下的状态是很难估计的。由于问题的复杂性，不可能制定适用于所有状况的规则.interrelationship内在关系texture结构density密度evaluate估计

Forexample,thesupportingpowerofsoilsincreaseswithdensity.Aroadconstructedonagivensoilmaybeentirelysatisfactoryifthesoilisproperlycompacted.Ontheotherhand,theroadmayfailifthesoilisinsufficientlycompacted,particularlyifthevoidsbecomefilledwithwater.

例如，随着密度的提高，土壤的支撑力增强。路修建在被适当压实的给定土体上那会是完全令人满意的。另一方面，如果土没有被充分压缩，特别是如果土体的孔隙充满了水，道路可能会失效。TranslatethefollowingsentencesintoChinese.highwayalignmentExercisesclover-leafinterchangecentrifugalforcecutawayviewmoisturetransitioncurveplanview4.苜蓿叶立体交叉5.缓和曲线8.离心力2.公路线形6.平面图3.路基1.湿度subgrade7.剖面图1.Inmodernpracticeitiscommontointerposetransitionorspiralcurvesbetweentangentsandcircularcurves.2.必须避免平地突然变化为急弯以及很长的切线后紧跟着锐曲线，否则就会产生事故风险。2.Suddenchangesfromflattosharpcurvesandlongtangentsfollowedbysharpcurvesmustbeavoided;otherwise,accidenthazardswillbecreated.1.目前在实际操作中，一般在切线和圆曲线之间插入缓和曲线和螺旋曲线。3.因为自然地形是不平坦的，为了得到平坦的道路，需要挖方和填方来改变自然地形。3.Becausenaturalterrainsareuneven,togetsmoothroad,cuttingandfillingareneededtochangethenaturalterrain.4.Soilsthathaveamplestrengthandsupportingpowerunderonesetofmoistureconditionsmaybeentirelyunsatisfacoryifthepercentageofmoisturechanges.5.另一方面，如果土没有被充分压缩，特别是如果土体的孔隙充满了水，道路可能会失效。5.Ontheotherhand,theroadmayfailifthesoilisinsufficientlycompacted,particularlyifthevoidsbecomefil