二级公路毕业设计外文文献

外文资料及翻译EffectsofDesignFeaturesonRigidPavementPerformanceTheperformanceofrigidpavementsisaffectedbyavarietyofdesignfeatures,includingslabthickness,basetype,jointspacing,reinforcement,jointorientation,loadtransfer,dowelbarcoatings,longitudinaljointdesign,jointsealant,tiedconcreteshoulders,andsubdrainage.AstudywasmadebyERESConsultants,Inc.underFHWAcontractontheeffectsofthesefeaturesonrigidpavementperformance.Ninety-fivepavementsectionslocatedinfourmajorclimaticregionswerethoroughlyevaluated.Thefollowingconclusions,whichprovidesomerevealinginsightsintopavementperformance,areabstractedfromthereport(Smithetal.,1990a).SlabThicknessTheeffectofslabthicknessonpavementperformancewassignificant.Itwasfoundthatincreasingslabthicknessreducedtransverseandlongitudinalcrackinginallcases.Thiseffectwasmuchmorepronouncedforthinnerslabsthanforthickerslabs.Itwasnotpossibletocomparetheperformanceofthethinnerslabsandthethickerslabsdirectly,becausethethickslabswereallconstructeddirectlyonthesubgradeandthethinnerslabswereallconstructedonabasecourse.Increasingthethicknessofslabdidnotappeartoreducejointspallingorjointfaulting.Thickslabsplaceddirectlyonthesubgrade,especiallyinwetclimatesandexposedtoheavytraffic,faultedasmuchasthinslabsconstructedonabasecourse.BaseTypeBasetypes,includingbase/slabinterfacefriction,basestiffness,baseerodibility,andbasepermeability,seemedtohaveagreateffectontheperformanceofjointedconcretepavements.Themajorperformanceindicators,whichwereaffectedbyvariationsinbasetype,weretransverseandlongitudinalcracking,jointspalling,andfaulting.Theworstperformingbasetype,consistedofthecement-treatedorsoilcementbases,whichtendedtoexhibitexcessivepumping,faulting,andcracking.Thisismostlikelyduetotheimperviousnatureofthebase,whichtrapsmoistureandyetcanbrea-kdownandcontributetothemovementoffinesbeneaththeslab.Theuseofleanconcretebasesgenerallyproducedpoorperformance.Largecurl-ingandwarpingstresseshavebeenassociatedwithslabsconstructedoverleanconcretebases.Thesestressesresultinconsiderabletransverseandlongitudinalcrackingoftheslab.Thepoorperformanceofthesebasescanalsobeattributedtoabathtubdesign,inwhichmoistureistrappedwithinthepavementcrosssection.Dense-gradedasphalt-treatedbasecoursesrangedinperformancefromverypoortogood.Thefactthatthesetypesofbaseswereoftenconstructedasabathtubdesigncontributedtotheirpoorperformance.Thisimproperdesignoftenresultedinseverecracking,faulting,andpumping.TheconstructionofthickerslabsdirectlyonthesubgradewithnobaseresultedInapavementthatperformedmarginally.Thesepavementswereespeciallysusceptibletofaulting,evenunderlowtrafficlevels.Pavementsconstructedoveraggregatebaseshadvariedperformance,butweregenerallyinthefairtoverygoodcategory.Ingeneral,themoreopen-gradedtheaggregate,thebettertheperformance.Anadvantageofaggregatebasesisthattheycontributetheleasttothehighcurlingandwarpingstressesintheslab.Eventhoughaggregatebasesarenotopen-graded,theyaremorepermeableandhavealowerfrictionfactorthanstabilizedbases.Thebestbasesintermsofpavementperformancewerethepermeablebases.Typicalbasecourseshavepermeabilitiesrangingfrom0tolessthan1ft/day(0.3m/day);goodpermeablebaseshavepermeabilitiesupto1000ft/day(305m/day).Specificareasofconcernwerethehighcornerdeflectionsandthelowloadtransferexhibitedbythepermeablebases.Thesecanaffecttheirlong-termperformance,sotheuseofdowelbarsmightberequired.AnunexpectedbenefitofusingpermeablebaseswasthereductioninDcrackingonpavementssusceptibletothistypeofdistress.SlabLengthForJPCP,thelengthofslabsinvestigatedrangedfrom7.75to30ft(2.4to9.1m).Itwasfoundthatreducingtheslablengthdecreasedboththemagnitudeofthejointfaultingandtheamountoftransversecracking.Onpavementswithrandomjointspacings,slabswithjointspacingsgreaterthan18ft(5.5m)experiencedmoretransversecrackingthandidtheshorterslabs.ForJRCP,thelengthofslabsinvestigatedrangedfrom21to78ft(6.4to23.9m).Generally,shorterjointspacingsperformedbetter,asmeasuredbythedeterioratedtransversecracks,jointfaulting,andjointspalling.However,severalJRCPwithlongjointspacingsperformedquitewell.Inparticular,thelongjointedpavementsinNewJersey,whichwereconstructedwithexpansionjoints,displayedexcellentperformance.Anexaminationofthestiffnessoffoundationwasmadethroughtheuseoftheradiusofrelativestiffness,f.Generallyspeaking,whentheratioL/E,whereListhelengthofslab,wasgreaterthan5,transversecrackingoccurredmorefrequently.Thisfactorwasfurtherexaminedfordifferentbasetypes.Itwasfoundthatstifferbasecoursesrequiredshorterjointspacingstoreduceoreliminatetransversecracking.ReinforcementTheamountofsteelreinforcementappearedtohaveaneffectincontrollingtheamountofdeterioratedtransversecracking.Pavementsectionswithlessthan0.1%reinforcingsteeloftendisplayedsignificantdeterioratedtransversecracking.Aminimumof0.1%reinforcingsteelisthereforerecommended,withlargeramountsrequiredformoresevereclimateandlongerslabs.JointOrientationConventionalwisdomhasitthatskewedjointspreventtheapplicationoftwowheelloadstothejointatthesametimeandthuscanreduceload-associateddistresses.Theresultsfromtheli