完整版有关隧道方面外文文献与翻译.docx

完整版有关隧道方面外文文献与翻译.docx

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完整版有关隧道方面外文文献与翻译

Aconvection-conductionmodelforanalysisofthefreeze-thaw

conditionsinthesurroundingrockwallofa

tunnelinpermafrostregions

HEChunxiong（何春雄）,

（StateKeyLaboratoryofFrozenSoilEngineering,LanzhouInstituteofGlaciologyand

Geocryology,

ChineseAcademyofSciences,Lanzhou730000,China;DepartmentofAppliedMathematics,

SouthChinaUniversityofTechnology,Guangzhou510640,China）

WUZiwang（吴紫汪）andZHULinnan（朱林楠）

（StatekeyLaboratoryofFrozenSoilEngineering,LanzhouInstituteofGlaciologyand

Geocryology

ChineseAcademyofSciences,Lanzhou730000,China）

ReceivedFebruary8,1999

Abstract

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

Keywords:

tunnelincoldregions,convectiveheatexchangeandconduction,freeze・thaw.

Anumberofhighwayandrailwaytunnelshavebeenconstructedinthepermafrost

regionsandtheirneighboringareasinChina.Sincethehydrologicalandthermalconditionschangedafteratunnelwasexcavated,thesurroundingwallrockmaterialsoftenfroze,thefrostheavingcauseddamagetothelinerlayersandseepingwaterfrozeintoicediamonds,whichseriouslyinterferedwiththecommunicationandtransportation.SimilarproblemsofthefreezingdamageinthetunnelsalsoappearedinothercountrieslikeRussia,NorwayandJapan.Henceitisurgenttopredictthefreeze-thawconditionsinthesurroundingrockmaterialsandprovideabasisforthedesign,constructionandmaintenaneeofnewtunnelsincoldregions.

Manytunnels,constructedincoldregionsortheirneighbouringarea,spassthroughthepartbeneaththepermafrostbase.Afteratunnelisexcavat,edtheoriginalthermodynamicalconditionsinthesurroundingsareandthawdestroyedandreplacedmainlybytheairconnectionswithouttheheatradiation,theconditionsdeterminedprincipallybythetemperatureandvelocityofairflowinthetunnel,thecoefficientsofconvectiveheattransferonthetunnelwall,andthegeothermalheat.Inordertoanalyzeandpredictthefreezeandthawconditionsofthesurroundingwallrockofatunnel,presumingtheaxialvariationsofairflowtemperatureandthecoefficientsofconvectiveheattransfer,LunardinidiscussedthefreezeandthawconditionsbytheapproximateformulaeobtainedbySham-sundarinstudyoffreezingoutsideacirculartubewithaxialvariationsofcoolanttemperature・Wesimulatedthetemperatureconditionsonthesurfaceofatunnelwallvaryingsimilarlytotheperiodicchangesoftheoutsideairtemperature.Infact,thetemperaturesoftheairandthesurroundingwallrockmaterialaffecteachothersowecannotfindthetemperaturevariationsoftheairflowinadvance;furthermore,itisdifficulttoquantifythecoefficientofconvectiveheatexchangeatthesurfaceofthetunnelwall・Thereforeitisnotpracticabletodefinethetemperatureonthesurfaceofthetunnelwallaccordingtotheoutsideairtemperature.Inthispaper,wecombinetheairflowconvectiveheatex-changeandheatconductioninthesurroundingrockmaterialintoonemode,Iandsimulatethefreeze-thawconditionsofthesurroundingrockmaterialbasedontheinsituconditionsofairtemperature,atmosphericpressure,windforceattheentryandexitofthetunnel,andtheconditionsofhydrogeologyandengineeringgeology.Mathematical

model

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

Sincethemonthly-averageairtemperatureisbeneathO'}Cforeightmonthsatthetunnelsiteeachyearandtheconstructionwouldlastforseveralyears,thesurroundingrockmaterialswouldbecomecoolerduringtheconstruction・Weconcludethat,afterexcavation,thepatternofairflowwoulddependmainlyonthedominantwindspeedattheentryandexit,andtheeffectsofthetemperaturedifferencebetweentheinsideandoutsideofthetunnelwouldbeverysmall.Sincethedominantwinddirectionisnortheastatthetunnelsiteinwinter,theairflowinthetunnelwouldgofromtheexittotheentry.Eventhoughthedominantwindtrendissoutheastlyinsummer,consideringthepressuredifference,thetemperaturedifferenceandthetopographyoftheentryandexi,ttheairflowinthetunnelwouldalsobefromtheexittoentry・Additionally,sincethewindspeedatthetunnelsiteislow,wecouldconsiderthattheairflowwouldbeprincipallylaminar.

Basedonthereasonsmentione,dwesimplifythetunneltoaroundtube,andconsiderthatthe

airflowandtemperaturearesymmetricalabouttheaxisofthetunnel,Ignoringtheinflueneeoftheairtemperatureonthespeedofairflow,weobtainthefollowingequation:

ra（/vav亠

X+7★亦…

at/r/Au-z—+（/—+dt%

wheret,x,rarethetime,axialandradialcoordinates;U,Vareaxialandradialwindspeeds;Tistemperature;pistheeffectivepressure（that,isairpressuredividedbyairdensity）;visthekinematicviscosityofair;aisthethermalconductivityofair;Listhelengthofthetunnel;Ristheequivalentradiusofthetunnelsection;Disthelengthoftimeafterthetunnelconstruction;

St（t）,Su（t）arefrozenandthawedpartsinthesurroundingrockmaterialsrespectively;f,uandCt,CUarethermalconductivitiesandvolumetricthermal

capacitiesinfrozenandthawedpartsrespectively;X=（x,r）,（t）isphasechangefront;Lhisheatlatentoffreezingwater;andToiscriticalfreezingtemperatureofrock（hereweassumeTo=-0.1C）.

2usedforsolvingthemodel

Equation

（1）showsflow.Wefirstsolvethoseconcerningtemperatureatthatthetemperatureofthesurroundingrockdoesnotaffectthespeedofairequationsconcerningthespeedofairflow,andthensolvethoseequationseverytimeelapse.2.

1Procedureusedforsolvingthecontinuityandmomentumequations

Sincethefirstthreeequationsin⑴arenotindependentwederivethesecondequationbyx

andthethirdequationbyr.Afterpreliminarycalculationweobtainthefollowing

ellipticequationconcerningtheeffectivepressurep:

Thenwesolveequationsin

（1）usingthefollowingprocedures:

（i）AssumethevaluesforUOVO;

（ii）substitutingUO,VOintoeq.

（2）,andsolving

（2）,weobtainpO;

（iii）solvingthefirstandsecondequationsof

（1）,weobtainUO,V1;

（iv）solvingthefirstandthirdequationsof

（1）,weobtainU2,V2;

（v）calculatingthemomentum-averageofU1,v1andU2,v2,weobtainthenewUO,VO;

thenreturnto（ii）;

（vi）iteratingasaboveuntilthedisparityofthosesolutionsintwoconsecutiveiterationsissufficientlysmallorissatisfied,wethentakethosevaluesofpOUOandVOastheinitialvaluesforthenextelapseandsolvethoseequationsconcerningthetemperature..

2.2Entiremethodusedforsolvingtheenergyequations

Asmentionedpreviously,thetemperaturefieldofthesurroundingrockandtheairflowaffecteachother.Thusthesurfaceofthetunnelwallisboththeboundaryofthetemperaturefieldinthesurroundingrockandtheboundaryofthetemperaturefieldinairflow.Therefore,itisdifficulttoseparatelyidentifythetemperatureonthetunnelwallsurface,andwecannotindependentlysolvethoseequationsconcerningthetemperatureofairflowandthoseequationsconcerningthetemperatureofthesurroundingrock.Inordertocopewiththisproblem,wesimultaneouslysolvethetwogroupsofequationsbasedonthefactthatatthetunnelwallsurfacebothtemperaturesareequal.Weshouldbearinmindthephasechangewhilesolvingthoseequationsconcerningthetemperatureofthesurroundingrockandtheconvectionwhilesolvingthoseequationsconcerningthetemperatureoftheairflow,andweonlyneedtosmooththoserelativeparametersatthetunnelwallsurface.Thesolvingmethodsfor

theequationswiththephasechangearethesameasinreferenee[3].

2.3Determinationofthermalparametersandinitialandboundaryconditions2.3.1Determinationofthethermalparameters.Usingp=1013.25-0.1088H,wecalculate

PairpressurepatelevationHandcalculatetheairdensityusingformula,

whereTistheyearly-averageabsoluteairtemperatureandGisthehumidityconstantofair.LettingCpbethethermalcapacitywithfixedpressure,thethermalconductivity,andthedynamicviscosityofairflow,wecalculatethethermalconductivityandofthesurroundingrockaredeterminedfromthetunnelsite.

kinematicviscosityusingtheformulasa—and—.Thethermalparameters

CP

2.3.2Determinationoftheinitialandboundaryconditions.Choosetheobservedmonthlyaveragewindspeedattheentryandexitasboundaryconditionsofwindspeed