受施工卸载扰动黄土的变形与强度特性研究

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1、第24卷第13期岩石力学与工程学报Vol.24No.132005年7月ChineseJournalofRockMechanicsandEngineeringJuly，2005受施工卸载扰动黄土的变形与强度特性研究12张孟喜，孙钧(1.上海大学土木工程系，上海200072；2.同济大学地下建筑与工程系，上海200092)摘要：各种施工活动都不同程度地对周围土体产生扰动影响，应力状态与应力路径的改变作为施工卸载的关键影响因素，对施工扰动起着主导作用。在分析基坑开挖及隧道与地下洞室掘进卸载作用的基础上，根据不同施工工况的特点，制定了室内非常规三轴卸载试验方案，

2、对不同卸载应力路径下的应力–应变关系曲线、强度与变形特性及破坏特征进行了一系列卸载试验研究。试验结果表明，卸载作用下的强度与变形特性、变形模量及破坏特征与加载路径存在很大差别，挤长破坏的抗剪强度较压缩破坏低，挤长破坏的最大轴向应变仅为压缩破坏的1/3～1/2。关键词：土力学；卸载；加载；土体扰动；应力路径；开挖中图分类号：P642.15文献标识码：A文章编号：1000–6915(2005)13–2248–07UNLOADING-INDUCEDDEFORMATIONANDSTRENGTHPROPERTIESOFLOESSDURINGCONSTRUCTION

3、12ZHANGMeng-xi，SUNJun(1.DepartmentofCivilEngineering，ShanghaiUniversity，Shanghai200072，China；2.DepartmentofGeotechnicalEngineering，TongjiUniversity，Shanghai200092，China)Abstract：Duringexcavatingtunnelsandsubwaytunnelwithshield，differentunloadingeffectsinconstructionoccurtodisturb

4、surroundingearthandadjacentbuildings.Thechangeofstressstateandstresspath，asaprincipalfactor，playsanimportantroleindisturbancecausedbyvariousconstructionactivities.Forexample，thestatesofstressandconsolidationatsidesandbottomofpitchangeduringexcavation.Intheprocessofshielding，earth

5、surroundingthegapsofshieldendstakesvariousunloadingeffectstoalterthestressstates.Thereexistcompressivedisturbancesintheearthrightinthefrontoftunneling.Thegapsbetweentheendofshieldandlininggiverisetomovingandloosenedearthtoformunloadingdisturbanceareas.Incurrenttheoriesofdesignand

6、calculations，loadingmodelsareusuallyappliedwithoutreallyconsideringtheunloadingeffectinexcavation.Besides，thefactorsofvariousconstructionmethods，indefinitenessofundergroundconstructionandcomplexityofsurroundingenvironmenthaveallcontributedtomakeundergroundconstructionasriskyproje

7、cts，whichhaverenderedseveraldisastrousaccidentsinrecentyearsthatjeopardizelifeandproperty，adjacentbuildings，undergroundpipelinesandinterruptintercommunicationsystems.Basedontheanalysisofunloadingeffectsindifferenttypesofconstructionandvariousconstructionconditions，thispaperpropos

8、essomelaboratorytestschemesforloesswithm