陈湘生：再说地层冻结法

再说地层冻结法——纪念地层冻结法150周年SomeNewWordsOnGroundFreezingMethod——inmemoryof150thanniversaryapplicationofGFM深圳市地铁集团有限公司陈湘生博士上海，05.2012CHENXiangsheng,Ph.D.ShenzhenMetroCo.(Group),Ltd.Shanghai,05.2012目录Contents1.概述Overview2.地层冻结法关键要素ThekeyelementsforGFM3.人工冻土力学参数试验注意事项Themainpointsfortestsofartificialfrozensoilmechanicalproperties4.地层冻胀融沉问题及对策Thecountermeasuretogroundfreezingheaveandthawsettlement5.最新地层冻结案例SomenewcasesinterestedofGFM1.概述Overview•追索求源Originating地层冻结法源于天然冻结现象。1850年代蒸汽压缩式冷冻机发明后，人类第一次使用地层冻结法是1862年在Wales基坑中；1880年德国工程师Poetch首先提出地层冻结法原理，并于1883年在德国阿尔巴里德煤矿成功地采用冻结工法建造103m深的竖井。我国第一次应用地层冻结法是1955年开滦煤矿林西风井（直径5m，冻深105m）。Groundfreezingmethod(GFM)originatedfromnaturalfreezingphenomenon.Itwasthefirsttimein1862thatGFMwasusedinWalesfoundationpitafterinventionofsteamcompressionrefrigeratorin1850s.TheGermanengineer,Poetch,proposedfirsttheprincipleofGFMin1880,andthenthismethodwassuccessfullyusedinsinkingashaftindepthof103minGermany'scoalminein1883.Itwasin1955thatGFMwasusedinsinkingLinxiairshaft(dia.5mandfrozendepthof105m)inKailuanCoalMinefirstinChina.1.概述Overview(Cont.)•核心是把地层里的水变成冰ThekeyofGFMistochangethewaterinsoilintoice.地层冻结的核心是把地层里几乎“没有强度”的水变成“强度极高且可以粘结土颗粒”的冰，而且冰的强度和弹性模量随负温度降低而增大。由此可以根据对冻土结构要求而随时调节冻结温度来确保冻土结构的稳定。ThecoreofGFMistochangenostrengthofwaterthestrataintoiceofhighstrengthandpowerbondingsoilparticle“.Moreover,bothstrengthandelasticitymodulusoficeincreasewithdecreaseinnegativetemperature.Thismay,accordingtotherequirementsoffrozensoilstructure,adjustthefreezingtemperatureinfrozensoilstructuretoensureit’sstabilityatanytime.1.概述Overview(Cont.)•核心是把地层里的水变成冰(Cont.)ThekeyofGFMistochangethewaterinsoilintoice.所以，要了解水冻成冰的要素：地层里水的冰点、含盐、地层温度、水力联系和周边影响温度的边界条件等，还有冻土结构相关连影响稳定的边界条件。在设计冻土结构时，要充分了解其受力状态、简化的受力模型、需要的力学指标等。还有土壤的冻胀和融沉特性Firstthingsfirstistounderstandthefreezingtemperatureofthewaterinthestratum,it’ssalt,stratumformationtemperature,hydraulicrelationshipandsurroundingheatinfluence,theboundaryconditionsoftemperature,andmoreovertheboundaryconditionsofthefrozenstructure.Thenalltheseelementsmustfullybeunderstoodwhenafrozenstructureisdesigned:itsstressstate,thesimplifiedmodel,themechanicsindexneeded,andetc.Meanwhile,thecharacteristicsmustbekeptinmindoffreezingheaveandthawsettlementofsoil.1.概述Overview(Cont.)•带领全球的中国地层冻结GroundGreezinginMainlandChina——Leadingtheglobal截至2011年年底，中国大陆地区利用地层冻结法完成凿井约790个，总里程约180km；最大冻结深度达到955m。完成市政工程冻结项目98个（其中地铁工程超过70个），最长水平冻结长度到达147m。各项指标领先全球。Bytheendof2011,GFMhassuccessfullybeenusedinChinamainlandsunkshafts790withtotalmileagemorethan180kmandmaximumfrozendepthof955m,andfinishedmunicipalengineeringprojects98(includingthesubwayfrozenprojectsmorethan70)withthelongesthorizontalfreezinglengthof147m.Alltechnicalindexesleadintheworld.2.地层冻结法关键要素ThekeyelementsforGFM工程地质和水文地质及关键物理力学指标Theinformationofengineeringgeologyandhydrogeology,andthekeyphysicalandmechanicalindexes设计要素Thekeyfactorsofdesign施工要素Thekeyelementsforexecution管理等关联要素Thekeypointsformanagement2.地层冻结法关键要素ThekeyelementsforGFM(cont.)•工程地质和水文地质及关键物理力学指标Theinformationofengineeringgeologyandhydrogeology,andthekeyphysicalandmechanicalindexes1.施工范围内及关联的地层分布、水位（含气?）含水层及水力联系、流速流向、含盐量、隔水层、土的基本力学性质、比热、热传导系数、潜热、结冰温度等Therelatedstratadistribution,stage(airball?),aquiferlocationandhydraulicconnection,Flowvelocityanddirection,saltconcentrationinthesoil,aquiclude,thebasicmechanicalpropertiesofsoil,specificheatandthermalconductivity,thelatentheat,freezingtemperature,etc2.土壤冻胀和融沉（冻土解冻）；单轴抗压、抗拉、抗剪(粘聚力、内摩擦角)、三轴强度、变形模量、泊淞比（受温度、含水量、未冻水含量、粒径、孔隙率、荷载、时间等影响）Frostheavingandthawsettlement(thawing);Uniaxialcompressive,tensileandshearstrength(cohesion,frictionangle),triaxialstrength,deformationmodulusandpoissonratio(influencedbytemperature,watercontent,unfrozenwatercontent,particlediameter,poreratio,loading,andloadedtime,etc)2.地层冻结法关键要素(cont.)ThekeyelementsforGFM•设计要素Thekeyfactorsofdesign首先是建立冻土结构受力模型（纯冻土结构、和其它结构共同承载、作为其它结构承载的封水等）Firststepistochoseafrozenstructurebearingmodel(purefrozensoilstructure,orotherstructurejointedwithfrozensoil,oraswatershutoff(frozensoil)forotherstructure)其次是在所选结构模型下全面考量全过程可能影响冻土强度、冻土结构本身可能影响周边环境或者影响维护结构本身稳定和安全的可能性Secondistocomprehensivelyconsiderthepossibilityofaffectingthepermafroststrengthinthechosenfrozenstructuremodelthroughtheprocess,frozensoilstructureitselfmayaffecttherelatedenvironmentorinfluencethestabilityandsecurityofthefrozenstructureitself.2.地层冻结法关键要素(cont.)ThekeyelementsforGFM设计要素Thekeyfactorsofdesign(cont.)再次是按所选冻土结构受力模型进行对应的冻土力学性能试验而获得必要的计算参数、并对冻土结构的冻胀融沉进行量化、针对计算结构进行措施补充（包括所有检测监控）Onceagainistoobtainthenecessaryparametersofthefrozensoilbycarryingoutthecorrespondingmechanicaltestaccordingtoselectedfrozensoilstructurebearingmodel,toquantitativelycalculatefreezingheaveandthawsettlementoftherelatedstrata,andtosupplementmeasuresforthefrozensoilstructure（includingallthedetectionmonitoring）最后就是实施这一设计进行施工组织设计Thelastistocarryouttheconstructionorganizationdesign.2.地层冻结法关键要素ThekeyelementsforGFM(cont.)•施工要素Thekeyelementsforexecution冻结孔施工、冻结管安装以及质量的检测；Freezingpipeholedrilling,thepipeinstallation,andthefinalresultinspection地层内温度检测和盐水等检测系统的可靠性；Inspe