软土地基基坑开挖降水时引起的周围地基的沉降分析

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1、上海交通大学硕士学位论文软土地基基坑开挖降水时引起的周围地基的沉降分析姓名：唐翠萍申请学位级别：硕士专业：岩土工程指导教师：沈水龙20070101上海交通大学硕士学位论文摘要基坑在各种条件变化时降水引起地面沉降的影响，这些条件为土层参数、井点深度等。计算结果表明竖向渗透系数对地面沉降的影响比水平向渗透系数对地面沉降的影响要小；贮水率对沉降的影响不太大，但潜水含水层和承压含水层的水头都随着贮水率的增加而减小；降水井深度增加，基坑内沉降量增加，而地下水水头的变化量随之减少；沉降量与抽水量成正比。计算分析中还分别考虑了抽取潜水和承压水的情况，分析得出抽取承压水的影响范围较潜水

2、大，但是当抽取承压水的时间较短时引起的沉降较抽取潜水小。关键词：基坑降水、三维有限元分析、渗流、地面沉降II上海交通大学硕士学位论文AbstractAnalysisofSettlementduetoWithdrawalofGroundwaterinandaroundFoundationPitABSTRACTThesoftsoildepositgenerallyhasabundanceofgroundwaterwithhighgroundwatertable.Whenadeepfoundationpitisexcavatedinthisdeposit,inordertoe

3、nsurethesafety,itisnecessarytopumpgroundwaterduringexcavation.Thegroundwaterpumpingcausesthetransientseepageofgroundwatertoformadrawdownconearoundthepit.Drawdownofthegroundwaterlevelwillcausetheincreaseofeffectivestressofsoiloutsidethepit.Consequently,thesoftclaywillconsolidateandsettlem

4、entwilloccuraroundthepit.Inthisstudy,thesettlementaroundpitduetothewithdrawalofgroundwaterwillbeanalyzed.Themaincontentandnewfindingsoftheworkareasfollows:(1)Afiniteelementmodel,inwhich,groundwaterseepageisanalyzedthreedimensionallyandsettlementiscalculatedverticallybyusingTerzhaghi’sone

5、dimensionalconsolidationtheory.TheproposedmodelwasemployedtoapracticalprojectofdewateringbeforetheexcavationoffoundationpitinShanghai.Themaximumcalculateddewatering-induced-settlementinthepitis0.235m.Themeasuredsettlementinthepitis0.25m.Thisindicatesthatthismodelcansimulatethefieldcasefa

6、irlywell.(2)Determinationofparameters:Theparametersincludinghydraulicconductivity,theporosity,andthecoefficientofspecificstorageofsoillayeraredeterminedfromfieldandlaboratorytests.ThehydraulicconductivitywasdeterminedbythefieldpermeabilitytestfollowingtheprocedureestablishedbytheShanghai

7、FoundationDesigncode.Theporositywascalculatedfromvoidratio,whichwasdeterminedfromphysicalpropertytestinlaboratory.ThecoefficientofspecificstoragewascalculatedIII上海交通大学硕士学位论文Abstractfromthecoefficientofvolumetriccompressibility.Forcohesivesoil,thecoefficientofvolumetriccom