隧道与城市轨道交通工程土木外文翻译原文和译文.docx

隧道与城市轨道交通工程土木外文翻译原文和译文.docx

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隧道与城市轨道交通工程土木外文翻译原文和译文

隧道与城市轨道交通工程土木外文翻译原文和译文

Aconvection-conductionmodelforanalysisofthefreeze-thaw

conditionsinthesurroundingrockwallofa

tunnelinpermafrostregions

Abstract

Basedontheanalysesoffundamentalmeteorologicalandhydrogeologicalconditionsatthesiteofatunnelinthecoldregions,acombinedconvection-conductionmodelforairflowinthetunnelandtemperaturefieldinthesurroundinghasbeenconstructed.Usingthemodel,theairtemperaturedistributionintheXiluoqiNo.2Tunnelhasbeensimulatednumerically.Thesimulatedresultsareinagreementwiththedataobserved.Then,basedontheinsituconditionsofsirtemperature,atmosphericpressure,windforce,hydrogeologyandengineeringgeology,theair-temperaturerelationshipbetweenthetemperatureonthesurfaceofthetunnelwallandtheairtemperatureattheentryandexitofthetunnelhasbeenobtained,andthefreeze-thawconditionsattheDabanshanTunnelwhichisnowunderconstructionispredicted.

Keywords:

tunnelincoldregions,convectiveheatexchangeandconduction,freeze-thaw.

AnumberofhighwayandrailwaytunnelshavebeenconstructedinthepermafrostregionsandtheirneighboringareasinChina.Sincethehydrologicalandthermalconditionschangedafteratunnelwasexcavated，thesurroundingwallrockmaterialsoftenfroze,thefrostheavingcauseddamagetothelinerlayersandseepingwaterfrozeintoicediamonds，whichseriouslyinterferedwiththecommunicationandtransportation.SimilarproblemsofthefreezingdamageinthetunnelsalsoappearedinothercountrieslikeRussia,NorwayandJapan.Henceitisurgenttopredictthefreeze-thawconditionsinthesurroundingrockmaterialsandprovideabasisforthedesign，constructionandmaintenanceofnewtunnelsincoldregions.

Manytunnels，constructedincoldregionsortheirneighbouringareas，passthroughthepartbeneaththepermafrostbase.Afteratunnelisexcavated，theoriginalthermodynamicalconditionsinthesurroundingsareandthawdestroyedandreplacedmainlybytheairconnectionswithouttheheatradiation,theconditionsdeterminedprincipallybythetemperatureandvelocityofairflowinthetunnel，thecoefficientsofconvectiveheattransferonthetunnelwall，andthegeothermalheat.Inordertoanalyzeandpredictthefreezeandthawconditionsofthesurroundingwallrockofatunnel，presumingtheaxialvariationsofairflowtemperatureandthecoefficientsofconvectiveheattransfer,LunardinidiscussedthefreezeandthawconditionsbytheapproximateformulaeobtainedbySham-sundarinstudyoffreezingoutsideacirculartubewithaxialvariationsofcoolanttemperature.Wesimulatedthetemperatureconditionsonthesurfaceofatunnelwallvaryingsimilarlytotheperiodicchangesoftheoutsideairtemperature.Infact，thetemperaturesoftheairandthesurroundingwallrockmaterialaffecteachothersowecannotfindthetemperaturevariationsoftheairflowinadvance;furthermore，itisdifficulttoquantifythecoefficientofconvectiveheatexchangeatthesurfaceofthetunnelwall.Thereforeitisnotpracticabletodefinethetemperatureonthesurfaceofthetunnelwallaccordingtotheoutsideairtemperature.Inthispaper,wecombinetheairflowconvectiveheatex-changeandheatconductioninthesurroundingrockmaterialintoonemodel，andsimulatethefreeze-thawconditionsofthesurroundingrockmaterialbasedontheinsituconditionsofairtemperature，atmosphericpressure，windforceattheentryandexitofthetunnel，andtheconditionsofhydrogeologyandengineeringgeology.

Mathematicalmodel

Inordertoconstructanappropriatemodel,weneedtheinsitufundamentalconditionsasaba-sis.HereweusetheconditionsatthesceneoftheDabanshanTunnel.TheDabanshanTunnelislo-totedonthehighwayfromXiningtoZhangye,southoftheDatongRiver,atanelevationof3754.78-3801.23m,withalengthof1530mandanalignmentfromsouthwesttonortheast.Thetunnelrunsfromthesouthwesttothenortheast.

Sincethemonthly-averageairtemperatureisbeneath0`Cforeightmonthsatthetunnelsiteeachyearandtheconstructionwouldlastforseveralyears，thesurroundingrockmaterialswouldbecomecoolerduringtheconstruction.Weconcludethat,afterexcavation,thepatternofairflowwoulddependmainlyonthedominantwindspeedattheentryandexit，andtheeffectsofthetemperaturedifferencebetweentheinsideandoutsideofthetunnelwouldbeverysmall.Sincethedominantwinddirectionisnortheastatthetunnelsiteinwinter,theairflowinthetunnelwouldgofromtheexittotheentry.Eventhoughthedominantwindtrendissoutheastlyinsummer,consideringthepressuredifference,thetemperaturedifferenceandthetopographyoftheentryandexit，theairflowinthetunnelwouldalsobefromtheexittoentry.Additionally，sincethewindspeedatthetunnelsiteislow，wecouldconsiderthattheairflowwouldbeprincipallylaminar.

Basedonthereasonsmentioned，wesimplifythetunneltoaroundtubeandconsiderthattheairflowandtemperaturearesymmetricalabouttheaxisofthetunnel，Ignoringtheinfluenceoftheairtemperatureonthespeedofairflow,weobtainthefollowingequation:

wheret，x，rarethetime，axialandradialcoordinates;U，Vareaxialandradialwindspeeds;Tistemperature;pistheeffectivepressurethatis，airpressuredividedbyairdensity;visthekinematicviscosityofair;aisthethermalconductivityofair;Listhelengthofthetunnel;Ristheequivalentradiusofthetunnelsection;Disthelengthoftimeafterthetunnelconstruction;，

t,tarefrozenandthawedpartsinthesurroundingrockmaterialsrespectively;,and,arethermalconductivitiesandvolumetricthermalcapacitiesinfrozenandthawedpartsrespectively;Xx,r，tisphasechangefront;Lhisheatlatentoffreezingwater;andToiscriticalfreezingtemperatureofrockhereweassumeTo-0.1℃.

usedforsolvingthemodel

Equation1showsflow.Wefirstsolvethoseconcerningtemperatureatthatthetemperatureofthesurroundingrockdoesnotaffectthespeedofairequationsconcerningthespeedofairflow,andthensolvethoseequationseverytimeelapse.

2.1Procedureusedforsolvingthecontinuityandmomentumequations

Sincethefirstthreeequationsin1arenotindependentwederivethesecondequationbyx

andthethirdequationbyr.Afterpreliminarycalculationweobtainthefollowingellipticequationconcerningtheeffectivepressurep:

Thenwesolveequationsin1usingthefollowingprocedures:

iAssumethevaluesforU0，V0;

iisubstitutingU0，V0intoeq.2，andsolving2，weobtainp0;

iiisolvingthefirstandsecondequationsof1，weobtainU0，V1;

ivsolvingthefirstandthirdequationsof1，weobtainU2，V2;

vcalculatingthemomentum-averageofU1，v1andU2，v2，weobtainthenewU0，V0;

thenreturntoii;

viiteratingasaboveuntilthedisparityofthosesolutionsintwoconsecutiveiterationsissufficientlysmallorissatisfied，wethentakethosevaluesofp0，U0andV0astheinitialvaluesforthenextelapseandsolvethoseequationsconcerningthetemperature..

2.2Entiremethodusedforsolvingtheenergyequations

Asmentionedpreviously，thetemperaturefieldofthesurroundingrockandtheairflowaffecteachother.Thusthesurfaceofthetunnelwallisboththeboundaryofthetemperaturefieldinthesurroundingrockandtheboundaryofthetemperaturefieldinairflow.Therefore，itisdifficulttoseparatelyidentifythetemperatureonthetunnelwallsurface，andwecannotindependentlysolvethoseequationsconcerningthetemperatureofairflowandthoseequationsconcerningthetemperatureofthesurroundingrock.Inordertocopewiththisproblem，wesimultaneouslysolvethetwogroupsofequationsbasedonthefactthatatthetunnelwallsurfacebothtemperaturesareequal.Weshouldbearinmindthephasechangewhilesolvingthoseequationsconcerningthetemperatureofthesurroundingrock，andtheconvectionwhilesolvingthoseequationsconcerningthetemperatureoftheairflow,andweonlyneedtosmooththoserelativeparametersatthetunnelwallsurface.Thesolvingmethodsfortheequationswiththephasechangearethesameasinreference[3].

2.3Determinationofthermalparametersandinitialandboundaryconditions.

Determinationofthethermalparameters.Usingp1013.25-0.1088H，wecalculateairpressurepatelevationHandcalculatetheairdensityusingformulaP／GTwhereTistheyearly-averageabsoluteairtemperature，andGisthehumidityconstantofair.Lettingbethethermalcapacitywithfixedpressure,thethermalconductivity，

andthedynamicviscosityofairflow,wecalculatethethermalconductivityandkinematicviscosityusingtheformulasand.Thethermalparametersofthesurroundingrockaredeterminedfromthetunnelsite.

2.3.2Determinationoftheinitialandboundaryconditions.Choosetheobservedmonthlyaveragewindspeedattheentryandexitasboundaryconditionsofwindspeed，andchoosetherelativeeffectivepressurep0attheexitthatis，theentryofthedominantwindtrendandonthesectionofentrythatis，theexitofthedominantwindtrend，wherekisthecoefficientofresistancealongthetunnelwall,d2R，andvistheaxialaveragespeed.WeapproximateTvaryingbythesinelawaccordingtothedataobservedatthesceneandprovideasuitableboundaryvaluebasedonthepositionofthepermafrostbaseandthegeothermalgradientofthethawrockmaterialsbeneaththepermafrostbase.

Asimulatedexample

Usingthemodelandthesolvingmethodmentionedabove，wesimulatethevaryinglawoftheairtemperatureinthetunnelalongwiththetemperatureattheentrya