道路与桥梁专业外文翻译、中英对照文档格式.doc
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专业名称:
土木工程专业(道路与桥梁)
年级班级:
道桥08-5班
学生姓名:
指导教师:
二○一二年五月十八日
河南理工大学本科毕业设计专业外文翻译
GeometricDesignofHighways
Theroadisonekindoflinearconstructionusedfortravel.Itismadeoftheroadbed,theroadsurface,thebridge,theculvertandthetunnel.Inaddition,italsohasthecrossingoflines,theprotectiveprojectandthetrafficengineeringandtheroutefacility.
Theroadbedisthebaseofroadsurface,roadshoulder,sideslope,sideditchfoundations.Itisstonematerialstructure,whichisdesignedaccordingtoroute'
splaneposition.Theroadbed,asthebaseoftravel,mustguaranteethatithastheenoughintensityandthestabilitythatcanpreventthewaterandothernaturaldisasterfromcorroding.
Theroadsurfaceisthesurfaceofroad.Itissingleorcomplexstructurebuiltwithmixture.Theroadsurfacerequirebeingsmooth,havingenoughintensity,goodstabilityandanti-slipperyfunction.Thequalityofroadsurfacedirectlyaffectsthesafe,comfortandthetraffic.
HighwaygeometrydesignstoconsiderHighwayHorizontalAlignment,VerticalAlignmenttwokindsoflinearandcross-sectionalcompositionofcoordination,butalsopayattentiontothesmoothflowofthelineofsight,etc.Determinetheroadgeometry,considerthetopography,surfacefeatures,rationaluseoflandandenvironmentalprotectionfactors,tomakefulluseofthehighwaygeometriccomponentsofreasonablesizeandthelinearcombination.
1.AlignmentDesign
Thealignmentofaroadisshownontheplaneviewandisaseriesofstraightlinescalledtangentsconnectedbycircular.Inmodernpracticeitiscommontointerposetransitionorspiralcurvesbetweentangentsandcircularcurves.
Alignmentmustbeconsistent.Suddenchangesfromflattosharpcurvesandlongtangentsfollowedbysharpcurvesmustbeavoided;
otherwise,accidenthazardswillbecreated.Likewise,placingcircularcurvesofdifferentradiiendtoend(compoundcurves)orhavingashorttangentbetweentwocurvesispoorpracticeunlesssuitabletransitionsbetweenthemareprovided.Long,flatcurvesarepreferableatalltimes,astheyarepleasinginappearanceanddecreasepossibilityoffutureobsolescence.However,alignmentwithouttangentsisundesirableontwo-laneroadsbecausesomedrivershesitatetopassoncurves.Long,flatcurvesshouldbeusedforsmallchangesindirection,asshortcurvesappearas“kink”.Alsohorizontalandverticalalignmentmustbeconsideredtogether,notseparately.Forexample,asharphorizontalcurvebeginningnearacrestcancreateaseriousaccidenthazard.
Avehicletravelinginacurvedpathissubjecttocentrifugalforce.Thisisbalancedbyanequalandoppositeforcedevelopedthroughcannotexceedcertainmaximums,andthesecontrolsplacelimitsonthesharpnessofcurvesthatcanbeusedwithadesignspeed.Usuallythesharpnessofagivencircularcurveisindicatedbyitsradius.However,foralignmentdesign,sharpnessiscommonlyexpressedintermsofdegreeofcurve,whichisthecentralanglesubtendedbya100-ftlengthofcurve.Degreeofcurveisinverselyproportionaltotheradius.
Tangentsectionsofhighwayscarrynormalcrossslope;
curvedsectionsaresuperelevated.Provisionmustbemadeforgradualchangefromonetotheother.Thisusuallyinvolvesmaintainingthecenterlineofeachindividualroadwayatprofilegradewhileraisingtheouteredgeandloweringtheinneredgetoproducethedesiredsuperelevationisattainedsomedistancebeyondthepointofcurve.
Ifavehicletravelsathighspeedonacarefullyrestrictedpathmadeupoftangentsconnectedbysharpcircularcurve,ridingisextremelyuncomfortable.Asthecarapproachesacurve,superelevationbeginsandthevehicleistiltedinward,butthepassengermustremainverticalsincethereisoncentrifugalforcerequiringcompensation.Whenthevehiclereachesthecurve,fullcentrifugalforcedevelopsatonce,andpullstherideroutwardfromhisverticalposition.Toachieveapositionofequilibriumhemustforcehisbodyfarinward.Astheremainingsuperelevationtakeseffect,furtheradjustmentinpositionisrequired.Thisprocessisrepeatedinreverseorderasthevehicleleavesthecurve.Wheneasementcurvesareintroduced,thechangeinradiusfrominfinityonthetangenttothatofthecircularcurveiseffectedgraduallysothatcentrifugalforcealsodevelopsgradually.Bycarefulapplicationofsuperelevationalongthespiral,asmoothandgradualapplicationofcentrifugalforcecanbehadandtheroughnessavoided.
Easementcurveshavebeenusedbytherailroadsformanyyears,buttheiradoptionbyhighwayagencieshascomeonlyrecently.Thisisunderstandable.Railroadtrainsmustfollowtheprecisealignmentofthetracks,andthediscomf