液氮地層凍結(jié)溫度場(chǎng)形成規(guī)律研究

液氮地層凍結(jié)溫度場(chǎng)形成規(guī)律研究液氮地層凍結(jié)溫度場(chǎng)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(chǎng)的形成規(guī)律仍然是一個(gè)問題，本文將深入研究并探討。

本文通過對(duì)已有文獻(xiàn)及實(shí)驗(yàn)數(shù)據(jù)的分析，總結(jié)出液氮地層凍結(jié)溫度場(chǎng)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(shí)間是影響液氮地層凍結(jié)溫度場(chǎng)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(shí)間越長(zhǎng)地面深度越大的溫度降低幅度越小；凍結(jié)時(shí)間較長(zhǎng)的滲透率較高的地層，由于地溫對(duì)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(chǎng)的控制因素是強(qiáng)制冷卻的液氮體積和密度。在相同的凍結(jié)時(shí)間下，液氮體積越大，密度越高，滲透率會(huì)降低，深埋地層的溫度降低幅度也會(huì)變小。最后，形成的溫度場(chǎng)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(chǎng)的形成規(guī)律。

關(guān)鍵詞：液氮地層凍結(jié)；溫度場(chǎng)；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