英翻中.docx
- 文档编号:25550288
- 上传时间:2023-06-09
- 格式:DOCX
- 页数:38
- 大小:500.91KB
英翻中.docx
《英翻中.docx》由会员分享,可在线阅读,更多相关《英翻中.docx(38页珍藏版)》请在冰豆网上搜索。
英翻中
EnglishLiterature
1MAINTENANCE
MaintenanceisafundamentalaspecttoconsiderinanyprojectinvolvingOGFCorPA,sincetheseactivitiescannotbeperformedinthesamewayasforconventionalDGHMA.ThefirstpartofthissectionreviewsthemainissuesassociatedwithwintermaintenanceinbothOGFCandEuropeanPAmaterials.Next,surfacemaintenanceisdiscussed,followedbyasummaryofcurrentrehabilitationpracticesforOGFCandPA.
1.1WinterMaintenance
Ingeneral,open-gradedmixturesexhibitlowerthermalconductivityandreducedheatcapacitycomparedwithDGHMA(18).ElevatedairvoidscontentsinOGFCreducetheflowrateofheatthroughthematerial.Infact,thethermalconductivityofOGFCcanbe40to70percentthemagnitudeofthatforDGHMA,makingOGFCoperateasan“insulatingcourse”atthesurface(16).
Asaresultofthesethermalproperties,thesurfaceofOGFCcanexhibittemperatures1to2°C(1.8to3.6°F)lowerthanthesurfacetemperatureofadjacentDGHMA,producingearlierandmorefrequentfrostandiceformation(6,16).Longerperiodsundersuchconditions,comparedwithDGHMA,arethusexpected.TheoccurrenceofthisphenomenoninPAhasbeenidentifiedinEurope(3,16),intheUnitedStates12,andspecificallyinTexas13.Thus,thetimetoreachadequatepavementfrictionvaluesaftericeformationhasoccurredislongerinporouspavement(16).Infact,formationofblackiceandextendedfrozenperiodsarecurrentlyconsideredthemainproblemsassociatedwithOGFCmaintenanceintheUnitedStates12.
Consequently,OGFCrequiresspecificwintermaintenancepractices.Forexample,inadditiontoconventionalpracticesforwintermaintenance,theuseofpavementconditionsensors,meteorologicalinstrumentation,andconnectinghardwareandsoftwareissuggestedtomonitortheroadsystemandsupportthedecisionprocessinvolvingwhenandhowtotreatanOGFCsurface(5).
Moresalt(ordeicingagents)andmorefrequentapplicationsthanonDGHMAarerequiredtoperformwintermaintenanceonOGFCandPA(15,16,18,32).InTexas13,deicingagentsarecurrentlyconsideredthemosteffectivewintertreatment,followedbyliquiddeiceragentsandsand.However,FHWArecommendsdevelopingsnowandicecontrolusingchemicaldeicersandplowingandavoidingtheuseofabrasivematerialstoimprovetraction(20).
Spreadingofsandtoenhancefrictionandhastendeicingcontributestothecloggingofvoids,causingadecreaseindrainageandnoisereductioncapabilities,whichareconsideredtwoofthemainOGFCadvantages(5).
SincethedeicercanflowintoanOGFCinsteadofremainingatthesurface,OregonDOThassuggestedresearchonorganicdeicerswithhigherviscosityandelectrostaticchargetechnology(similartothatemployedinemulsifiedasphalt)toimprovebondingofdeicersonthesurface(15).
IntensiveapplicationofliquiddeicingsaltshasallowedBelgiumtoobtainsimilarconditionsbetweendenseandporousmixturessubjectedtosnowyweather.Further,higherfrequencyofapplicationand25percentmoreliquidsaltingarereportedinTheNetherlandstoaddresswintermaintenancedifficultiesinPA(3,6).Furthermore,theuseofliquidchloridesolutionswasreportedinthecoldAlpineregionsofItaly,Austria,andSwitzerlandasmoreeffectivethantheuseofsolidsalt(5).Onthecontrary,aJapanesestudyconcludedthatfundamentalmodificationsarenotrequiredtopracticewintermaintenanceinPAsurfaces,sinceconsiderabledifferencesbetweenthesemixturesandDGHMAwerenotfound(33).
BritainpracticespreventivesaltingjustbeforesnowfallandmorefrequentapplicationofsaltincomparisonwithDGHMA(18).TheyrecommendincreasingtheamountofsaltappliedonDGHMAsectionsthatareadjacenttoPAsegments.ThisrecommendationisduetothereductioninthetransferofsaltfromthePAtotheDGHMAandthedifferencesinresponseofeachmaterial.Additionally,theyproposepromptplowingofsnowusingplowsfittedwithrubberedgesontheblades(topreventsurfacedamage).Finally,greatercontrolinthehomogeneousapplicationofdeicingchemicalisrequiredinOGFC,asthetraffichasminimalcontributioninitsdistributionovertheOGFCsurface(5).
1.2SurfaceMaintenance
AccordingtoasurveyconductedaspartoftheNationalCooperativeHighwayResearchProgram(NCHRP)Synthesis284,therearenoreportsintheUnitedStatesontheapplicationofmajormaintenanceforOGFC.From17statesthatreportedtheuseofOGFC,onlyNewMexico,Wyoming,SouthCarolina,andOregonemployfogsealstoperformpreventivemaintenance.
AlthoughquantitativeinformationaboutthesignificanceofthesetreatmentswhenappliedtoPAisnotavailable,itisexpectedthatfogsealsextendthelifeofporousmixturessincetheyprovideasmallfilmofunagedasphaltatthesurface(15).FHWArecommendsfogsealapplicationintwopasses(atarateof0.05gal/yd2foreachpass)usinga50percentdilutionofasphaltemulsionwithoutanyrejuvenatingagents(20).
ResearchinOregonregardingpermeabilityreductionandchangesinpavementfrictiononcertainOGFCpavementsgeneratedbyfogsealsconcludedthatthemixturesstillretainporosityandkeeptheroughtexturerelatedtoitscapabilitytoreducethepotentialforhydroplaning(15).However,quantitativeconclusionsregardingthechangesintheseparametersarenotincluded.Adecreaseinpavementfrictionwasnoticedimmediatelyafterfogsealapplication,butduringthefirstmonth,itincreasedconsiderablybytrafficaction.
SnowplowbladeabrasionhasconsiderableeffectsonthedurabilityoftrafficmarkingsonOGFC.Thermoplasticmarkingsorevensomefragmentsofmixtureimpregnatedwiththermoplasticcanbedisplacedwhensteelsnowplowbladesareusedforwintermaintenance.
FieldtrialsinRhodeIslandshowedthelackofdurabilityofthepermanentinlaidtrafficmarkingtapeonmodifiedOGFCundersuchconditions.Therefore,theyrecommendedsuspensionoftheuseofpermanentinlaidtrafficmarkingtapeuntilcorrectionscanbeimplementedtoimprovedurability(34).
RhodeIslandfurtherreportedthatrecessedthermoplastictrafficmarkingsprovedcosteffectiveincomparisonwithnon-recessedthermoplasticmarkings.Althoughrecessedthermoplastictrafficmarkingsshowedlowersnowplowbladedamage,fullyandsemi-recessedmarkingsinstalledinatangenthighwaytestsectionfailedtomaintaintherecommendedminimumretroreflectivityinwetnightconditions.Thisresultwasassociatedwiththeeffectofthewaterfilmpresentinthetangentsectionbutwasirrelevantinthesuper-elevatedcurvedtestsectionincludedintheresearch(34).
HighwayagenciesinBritishColumbia,SouthCarolina,andMarylandreportedthatthermoplasticmarkingmaterialwasthemostappropriateforOGFCapplications(16).TheBritishlimittheuseofpavementmarkingswiththermoplasticmaterialstocertaindirectionalsignsandarrows,consideringthatonPAthemarkingmaterialhasmoreopportunitytoflowdownwardintothemixture(18).AlthoughhigherdemandofmarkingmaterialinOGFC(duetohigherporosity)wasreportedbysomeagenciesintheUnitedStates(e.g.,Ohio,NewYork,andOregon),therewerenospecificrecommendationsregardingmaterialsfortrafficmarking(16).
CleaningofOGFCintheUnitedStatesisnotcommonpractice.ThisapproachindicatesthatlocalagenciesacceptthatOGFCfunctionalitycanbemaintainedduetoitsauto-cleaningcapacitycreatedinhighwayswithrelativelyhighspeedandhighvolumesoftrafficbythesuctiongeneratedbytiresrollingontheOGFC(5).
High-pressurewashingiscurrentlyquiteexpensiveandofquestionablevalue.CurrentmaintenanceactivitiesinDenmarkincludecleaningofthevoidsbyhigh-pressurewaterandairsuctiontwiceayearasastrategythatcombinestheconstructionoftwo-layerdrainageasphaltandcleaninginordertomaintainporosityduringthepavementlifetime(11).Ingeneral,EuropeanpracticelimitsplacingofPAonhighwayswithspeedshigherthan50km/h(31mph)tohelpinkeepingthesurfaceclean(10).
Ontheotherhand,Japanisapplyingthe“functionmaintenance”conceptthatcomprisesmorefrequentcleaningoperationswithonlypartialdebrisremovalduringeachcleaning(31).
1.3CorrectiveSurfaceMaintenance
MillandinlayusingOGFCwasrecommendedinOregontorepairOGFCwhenthequantitiesofmaterialwereenoughtojustifytheseactivities.Ifonlyasmallquantityisneeded,DGHMAissuggestedforpatching(15).FHWAadvisesonetoconsidertheareaandthedrainagecontinuity(20).Thus,whentheareatoberepairedissmallandtheflowaroundthepatchcanbeensured,DGHMAisrecommendedforpatching.Otherwise,thezoneshouldberepairedbyusingOGFCmixture.Nonetheless,in2000,theuseofDGHMAtorepairdelaminatedareasandpotholeswasindicatedbyallstatesintheUnitedStatesthatreportedtheutilizationofOGFC.CrackfillingwasreportedonlybyWyomingDOT,andaccordingtotheirexperience,drainageproblemscanresultfromcracksealing,sincewaterflowinsidethematerial
isdiminished(16).
InBritain,theuseofPAoropen-gradedmacadamisrecommendedtorepairbothsmallandlargepotholes.Theuseofdensebitumenmacadamispermitted,ifnecessary,butitsreplacementbypermeablemixtureisrecommended.Finally,theapplicationofhot-rolledasphalt(HRA)islimitedforrepairingsmallareas(i.e.,ontheorderof0.50m×0.50m[1.64feet×1.64feet]maximum)(18).
TodiminishthewheelimpactonthepatchjointandfacilitatetheflowofwateraroundaDGHMApatch,rotationofthepatchto45degreestoprovideadiamondshapeisrecommended.
Alternatively,theexecutionofmachinepatch,bladepatch,orscreedpatchmaybeused
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 英翻中