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.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.
AnumberofhighwayandrailwaytunnelshavebeenconstructedinthepermafrostregionsandtheirneighboringareasinChina.Sincethehydrologicalandthermalconditionschangedafteratunnelwasexcavated,thesurroundingwallrockmaterialsoftenfroze,thefrostheavingcauseddamagetothelinerlayersandseepingwaterfrozeintoicediamonds,whichseriouslyinterferedwiththecommunicationandtransportation.SimilarproblemsofthefreezingdamageinthetunnelsalsoappearedinothercountrieslikeRussia,NorwayandJapan.Henceitisurgenttopredictthefreeze-thawconditionsinthesurroundingrockmaterialsandprovideabasisforthedesign,constructionandmaintenanceofnewtunnelsincoldregions.
Manytunnels,constructedincoldregionsortheirneighbouringarea,spassthroughthepartbeneaththepermafrostbase.Afteratunnelisexcavat,edtheoriginalthermodynamicalconditionsinthesurroundingsareandthawdestroyedandreplacedmainlybytheairconnectionswithouttheheatradiation,theconditionsdeterminedprincipallybythetemperatureandvelocityofairflowinthetunnel,thecoefficientsofconvectiveheattransferonthetunnelwall,andthegeothermalheat.Inordertoanalyzeandpredictthefreezeandthawconditionsofthesurroundingwallrockofatunnel,presumingtheaxialvariationsofairflowtemperatureandthecoefficientsofconvectiveheattransfer,LunardinidiscussedthefreezeandthawconditionsbytheapproximateformulaeobtainedbySham-sundarinstudyoffreezingoutsideacirculartubewithaxialvariationsofcoolanttemperature.Wesimulatedthetemperatureconditionsonthesurfaceofatunnelwallvaryingsimilarlytotheperiodicchangesoftheoutsideairtemperature.Infact,thetemperaturesoftheairandthesurroundingwallrockmaterialaffecteachothersowecannotfindthetemperaturevariationsoftheairflowinadvance;furthermore,itisdifficulttoquantifythecoefficientofconvectiveheatexchangeatthesurfaceofthetunnelwall.Thereforeitisnotpracticabletodefinethetemperatureonthesurfaceofthetunnelwallaccordingtotheoutsideairtemperature.Inthispaper,wecombinetheairflowconvectiveheatex-changeandheatconductioninthesurroundingrockmaterialintoonemode,landsimulatethefreeze-thawconditionsofthesurroundingrockmaterialbasedontheinsituconditionsofairtemperature,atmosphericpressure,windforceattheentryandexitofthetunnel,andtheconditionsofhydrogeologyandengineeringgeology.Mathematicalmodel
Inordertoconstructanappropriatemodel,weneedtheinsitufundamentalconditionsasaba-sis.HereweusetheconditionsatthesceneoftheDabanshanTunnel.TheDabanshanTunnelislo-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,Ignoringtheinfluenceoftheairtemperatureonthespeedofairflow,weobtainthefollowingequation:
0 ra(/vav亠 X+7★亦… at/TI^u-z—+(/—+ dt% wheret,x,rarethetime,axialandradialcoordinates;U,Vareaxialandradialwindspeeds;Tistemperature;pistheeffectivepressure(that,isairpressuredividedbyairdensity);visthekinematicviscosityofair;aisthethermalconductivityofair;Listhelengthofthetunnel;Ristheequivalentradiusofthetunnelsection;Disthelengthoftimeafterthetunnelconstruction; Sf(t),Su(t)arefrozenandthawedpartsinthesurroundingrockmaterialsrespectively;f,uandCf,Cuarethermalconductivitiesandvolumetricthermal capacitiesinfrozenandthawedpartsrespectively;X=(x,r),(t)isphasechange front;Lhisheatlatentoffreezingwater;andToiscriticalfreezingtemperatureofrock(hereweassumeTo=-0.1C). 2usedforsolvingthemodel Equation (1)showsflow.Wefirstsolvethoseconcerningtemperatureatthatthetemperatureofthesurroundingrockdoesnotaffectthespeedofairequationsconcerningthespeedofairflow,andthensolvethoseequationseverytimeelapse.2.1Procedureusedforsolvingthecontinuityandmomentumequations Sincethefirstthreeequationsin (1)arenotindependentwederivethesecond equationbyx andthethirdequationbyr.Afterpreliminarycalculationweobtainthefollowing ellipticequationconcerningtheeffectivepressurep: 「艺p,丄空仃肚、J裂工r3r\dr)~t卄升 10 3Uav\2VZ nJ"Q・ (2) »0 Thenwesolveequationsin (1)usingthefollowingprocedures: (i)AssumethevaluesforU0V0; (ii)substitutingU0,V0intoeq. (2),andsolving (2),weobtainp0; (iii)solvingthefirstandsecondequationsof (1),weobtainU0,V1; (iv)solvingthefirstandthirdequationsof (1),weobtainU2,V2; (v)calculatingthemomentum-averageofU1,v1andU2,v2,weobtainthenew U0,V0; thenreturnto(ii); (vi)iteratingasaboveuntilthedisparityofthosesolutionsintwoconsecutiveiterationsissufficientlysmallorissatisfied,wethentakethosevaluesofp0U0and V0astheinitialvaluesforthenextelapseandsolvethoseequationsconcerningthetemperature.. 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. 2.3.2Determinationoftheinitialandboundaryconditions.Choosetheobservedmonthlyaveragewindspeedattheentryandexitasboundaryconditionsofwindspeed
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