液氮地層凍結(jié)溫度場形成規(guī)律研究

液氮地層凍結(jié)溫度場形成規(guī)律研究液氮地層凍結(jié)溫度場形成規(guī)律研究

摘要：隨著現(xiàn)代工程建設(shè)向地下深部的發(fā)展，液氮地層凍結(jié)技術(shù)作為一種有效的圍巖加固技術(shù)被廣泛應(yīng)用。然而，液氮地層凍結(jié)溫度場的形成規(guī)律仍然是一個問題，本文將深入研究并探討。

本文通過對已有文獻及實驗數(shù)據(jù)的分析，總結(jié)出液氮地層凍結(jié)溫度場的基本形式及其影響因素。首先，液氮溫度、滲透率與凍結(jié)時間是影響液氮地層凍結(jié)溫度場的主要因素。液氮溫度是調(diào)節(jié)凍結(jié)速度的重要因素；滲透率較低的地層，由于液氮注入后的均勻分布程度較高，時間越長地面深度越大的溫度降低幅度越??；凍結(jié)時間較長的滲透率較高的地層，由于地溫對液氮的溫度影響較大，導(dǎo)致地面深度越大的溫度降低幅度越大。其次，深埋地層凍結(jié)溫度場的控制因素是強制冷卻的液氮體積和密度。在相同的凍結(jié)時間下，液氮體積越大，密度越高，滲透率會降低，深埋地層的溫度降低幅度也會變小。最后，形成的溫度場也與地層材料的熱導(dǎo)率、熱容以及溫度歷史有關(guān)。這些因素綜合作用導(dǎo)致了液氮地層凍結(jié)溫度場的形成規(guī)律。

關(guān)鍵詞：液氮地層凍結(jié)；溫度場；形成規(guī)律

Abstract:Withthedevelopmentofmodernengineeringconstructiontodeepunderground,liquidnitrogengroundfreezingtechnologyhasbeenwidelyusedasaneffectiverockreinforcementtechnology.However,theformationlawofliquidnitrogengroundfreezingtemperaturefieldisstillaproblem,whichwillbedeeplystudiedandexploredinthispaper.

Throughtheanalysisofexistingliteratureandexperimentaldata,thispapersummarizesthebasicformofliquidnitrogengroundfreezingtemperaturefieldanditsinfluencingfactors.Firstly,thetemperatureofliquidnitrogen,permeabilityandfreezingtimearethemainfactorsaffectingtheliquidnitrogengroundfreezingtemperaturefield.Thetemperatureofliquidnitrogenisanimportantfactorinregulatingfreezingspeed;forformationswithlowpermeability,theuniformdistributiondegreeofliquidnitrogenafterinjectionishigh,andthetemperaturedropamplitudedecreasesasthedepthofthegroundincreaseswithtime;forformationswithlongfreezingtimeandhighpermeability,thetemperaturedropamplitudeatgreaterdepthofthegroundislargerduetotheinfluenceofgeothermalonthetemperatureofliquidnitrogen.Secondly,thecontrolfactorsofdeepburiedgroundfreezingtemperaturefieldarethevolumeanddensityofforcedcoolingliquidnitrogen.Underthesamefreezingtime,thelargerthevolumeandhigherdensityofliquidnitrogen,thelowerthepermeability,andthesmallerthetemperaturedropamplitudeofdeepburiedformation.Finally,theformationoftemperaturefieldisalsorelatedtothethermalconductivity,specificheatandtemperaturehistoryoftheformationmaterial.Thesefactorscombinedleadtotheformationlawofliquidnitrogengroundfreezingtemperaturefield.

Keywords:liquidnitrogengroundfreezing;temperaturefield;formationlaLiquidnitrogengroundfreezingisawidelyusedmethodforstabilizingsoilsandstructuresinconstructionprojects.Thetemperaturefieldgeneratedduringthisprocessplaysanimportantroleinachievingthedesiredresults.Theformationlawofthetemperaturefielddependsonseveralfactors,includingthevolumeanddensityofliquidnitrogenused,thepermeabilityoftheformation,andtheformationmaterial'sthermalconductivity,specificheat,andtemperaturehistory.

Oneofthesignificantfactorsaffectingthetemperaturefieldinliquidnitrogengroundfreezingisthevolumeanddensityoftheliquidnitrogenused.Ithasbeenobservedthatthelargerthevolumeandhigherdensityoftheliquidnitrogen,thelowerthepermeabilityoftheformation.This,inturn,leadstoasmallertemperaturedropamplitudeinthedeepburiedformation.Therefore,thevolumeanddensityofliquidnitrogenusedshouldbecarefullyselectedtoachievethedesiredtemperaturefield.

Anotherimportantfactoraffectingthetemperaturefieldisthepermeabilityoftheformation.Thelowerthepermeabilityofthematerial,thelowerthetemperaturedropamplitudeduetothereducedpenetrationoftheliquidnitrogen.Therefore,materialswithhigherpermeabilityrequirelargeramountsofliquidnitrogentoachievethedesiredtemperaturefield.

Thethermalconductivityandspecificheatoftheformationmaterialalsoplayacrucialroleintheformationlawofthetemperaturefield.Materialswithhigherthermalconductivityandspecificheatwillrequiremoreliquidnitrogentoachievethedesiredtemperaturedropamplitude.

Finally,thetemperaturehistoryoftheformationmaterialalsoaffectstheformationlawofthetemperaturefield.Thetemperaturehistorycanaffecttherateofcoolingandthedurationofthecoolingprocess,therebyaffectingthefinaltemperaturefield.

Insummary,theformationlawofthetemperaturefieldinliquidnitrogengroundfreezingdependsonseveralfactors,includingthevolumeanddensityoftheliquidnitrogenused,thepermeabilityoftheformation,andtheformationmaterial'sthermalconductivity,specificheat,andtemperaturehistory.ProperselectionofthesefactorscanensurethedesiredtemperaturefieldisachievedLiquidnitrogengroundfreezingisawidelyusedtechniqueingeotechnicalengineeringforachievinggroundstabilization,reducingsoilsettlements,andcontrollingthewaterinflowduringconstruction.Themethodworksbycirculatingliquidnitrogenthroughaseriesofinjectionwellsdrilledintothegroundtocreateafrozenbarrierthatpreventswatermigrationintotheexcavation.Thetemperaturefieldthatresultsfromthegroundfreezingprocesscansignificantlyaffectthesuccessoftheproject,andseveralfactorsinfluenceitsformation.

Oneoftheprimaryfactorsaffectingthetemperaturefieldisthevolumeanddensityoftheliquidnitrogenused.Thevolumeofliquidnitrogeninjectedintotheformationaffectsthedurationofthecoolingprocessandthesizeofthefrozenzonethatformsaroundtheinjectionwells.Alargervolumeofliquidnitrogenresultsinamoreextensivefrozenzone,whileasmallervolumecreatesathinnerfrozenbarrier.Densityalsoplaysaroleintheoveralleffectivenessofthegroundfreezingprocess.Ahigherdensityofliquidnitrogencancooltheformationmoreeffectively,resultinginamoreextensivefrozenzone.

Thepermeabilityoftheformationmaterialisanothercriticalfactorintheformationofthetemperaturefieldduringgroundfreezing.Permeablematerialslikesandorgravelcanallowtheliquidnitrogentoflowthroughtheformationmorequickly,resultinginafastercoolingprocessandamoreextensivefrozenzone.Incontrast,lesspermeablematerialssuchasclayorshalecanslowdownthecoolingprocess,resultinginasmallerfrozenbarrier.

Thethermalconductivity,specificheat,andtemperaturehistoryoftheformationmaterialalsoplayanessentialroleintheformationofthetemperaturefield.Thethermalconductivityofthematerialreferstohowwellitconductsheat.Materialswithhigherthermalconductivitycantransferheatmoreefficientlyandaremoreresponsivetothecoolingeffectsoftheliquidnitrogen.Thespecificheatofthematerialreferstohowmuchenergyisrequiredtoraiseitstemperature.Materialswithalowerspecificheatrequirelessenergytocooldownandaremoreresponsivetothegroundfreezingprocess.

Finally,thetemperaturehistoryoftheformationmaterialcaninfluenceitsresponsetocooling.Formationsthathaveexperiencedtemperaturechangesinthepastmaybemoreresistanttofreezing,whilethosethatarerelativelystablemaybemoreresponsivetogroundfreezing.

Inconclusion,achievingthedesiredtemperaturefieldduringliquidnitrogengroundfreezingrequirescarefulconsiderationofseveralfactors,includingthevolumeanddensityoftheliquidnitrogenused,thepermeabilityoftheformationmaterial,anditsthermalconductivity,specificheat,andtemperaturehistory.Byunderstandingthesefactorsandselectingappropriateparameters,engineerscanensurethesuccessofgroundfreezingprojectsandachievethedesiredresultsAnotherimportantfactortoconsiderduringliquidnitrogengroundfreezingisthesafetyhazardsassociatedwithhandlingandstoringliquidnitrogen.Liquidnitrogenisacryogenicfluidwithaboilingpointof-196°C,anditcancauseseverefrostbiteorthermalburnsifitcomesintocontactwithskin.Moreover,therapidreleaseofnitrogengasduringgroundfreezeoperationscancreateanoxygen-deficientenvironmentthatcanbedangeroustoworkers.

Tominimizethesesafetyhazards,engineersshouldensurethatworkershandlingliquidnitrogenareproperlytrainedinitssafeuseandhandling.Additionally,appropriatepersonalprotectiveequipment,suchasglovesandeyeprotection,shouldbewornbyworkersduringgroundfreezeoperations.Thestorageandtransportofliquidnitrogenshouldalsobecarriedoutinaccordancewithestablishedsafetyprocedures,includingtheuseofspecializedcontainersthataredesignedtominimizetheriskofspillsandleaks.

Furthermore,thereareseveralenvironmentalconsiderationsthatmustbetakenintoaccountwhenusingliquidnitrogenforgroundfreezing.Inparticular,thereleaseofnitrogengasduringgroundfreezeoperationscancontributetoairpollutionandclimatechange.Tominimizetheseenvironmentali