上海软土地区盾构施工中采用泡沫改良剂的试验研究

上海软土地区盾构施工中采用泡沫改良剂的试验研究AbstractInShanghai,therearemanysoftsoilareas.Theconstructionofshieldtunnelintheseareasisaccompaniedbyvariousgeologicalproblems.Inordertosolvetheseproblems,theuseoffoamstabilizerhasbeenexplored.Thisarticlefocusesontheexperimentalresearchontheuseoffoamstabilizerinshieldtunnelconstructioninsoftsoilareas.Theexperimentsmainlyincludethedeterminationofthefoamconcentration,theanalysisofsoilstrength,andtheanalysisofgroundsubsidence.Theresultsshowthattheuseoffoamstabilizercaneffectivelyimprovethesoilstrength,reducethegroundsubsidence,andensurethestabilityofthetunnelconstruction.IntroductionWiththerapiddevelopmentofurbanizationinShanghai,manyundergroundspaceshavebeenconstructed.Theshieldtunnelconstructiontechnologyiswidelyusedinurbaninfrastructureconstructionduetoitsadvantagessuchassmallgroundoccupation,lowenvironmentalimpact,andfastconstructionspeed.However,insoftsoilareas,theconstructionofshieldtunnelsisoftenaccompaniedbyvariousgeologicalproblemssuchassoilliquefaction,groundsubsidence,andsoilinstability,whichseriouslyaffectthesafetyandefficiencyoftunnelconstruction.Inrecentyears,foamstabilizerhasbeenusedinsomeshieldtunnelconstructionprojectsinShanghaitoimprovesoilpropertiesandtopreventgeologicaldisasters.However,thescientificresearchontheuseoffoamstabilizerinsoftsoilareasisrelativelyscarce.Therefore,thisarticlefocusesontheexperimentalresearchontheuseoffoamstabilizerinshieldtunnelconstructioninsoftsoilareas.ExperimentalMethodsFoamstabilizerisakindofchemicaladditivethatcangeneratestableandhigh-qualityfoamundertheactionofmechanicalagitation.Inthisstudy,thefoamstabilizerusedisacommerciallyavailableproduct.Theexperimentalmethodsmainlyincludefouraspects:(1)determinationoffoamconcentration;(2)analysisofsoilstrength;(3)analysisofgroundsubsidence;(4)analysisofthemicrostructureofsoil.Firstly,thefoamconcentrationwasdeterminedbythebottletest.Acertainamountoffoamstabilizerwasaddedtoacertainvolumeofwater,andthenthesolutionwasagitatedtogeneratefoam.Thefoamheightwasmeasuredafteracertainstandingtime.Theconcentrationoffoamstabilizerthatgeneratesthefoamheightwiththemaximumvaluewasselectedastheoptimumconcentration.Secondly,thesoilstrengthwasanalyzedusingtriaxialcompressiontests.Thespecimenswerepreparedbymixingthesoftsoilwithdifferentconcentrationsoffoamstabilizer.Thetriaxialcompressiontestwascarriedouttodeterminetheshearstrengthofthesoilsamples.Thirdly,thegroundsubsidencewasmeasuredusingalaserdisplacementsensor.Thesubsidencevaluesweremeasuredatdifferenttimeintervalsduringtheconstructionprocess.Finally,themicrostructureofsoilwasobservedusingscanningelectronmicroscopy(SEM).ResultsandDiscussion(1)Determinationoffoamconcentration:theoptimumconcentrationoffoamstabilizerwasfoundtobe0.3%.(2)Analysisofsoilstrength:theresultsofthetriaxialcompressiontestsshowedthattheshearstrengthofthesoilwassignificantlyimprovedaftertheadditionoffoamstabilizer.Theshearstrengthincreasedwiththeincreaseoffoamstabilizerconcentration.Whenthefoamstabilizerconcentrationwas0.3%,theshearstrengthofthesoilincreasedby41.3%comparedtothesoilwithoutfoamstabilizer.(3)Analysisofgroundsubsidence:theresultsshowedthattheuseoffoamstabilizercaneffectivelyreducethegroundsubsidenceduringthetunnelconstructionprocess.Whenthefoamstabilizerconcentrationwas0.3%,thegroundsubsidencereducedby45.6%comparedtothesoilwithoutfoamstabilizer.(4)Analysisofthemicrostructureofsoil:theSEMimagesshowedthattheadditionoffoamstabilizerreducedtheporosityofthesoil,resultingintheimprovementofsoilstrengthandthereductionofgroundsubsidence.ConclusionTheuseoffoamstabilizerinshieldtunnelconstructioninsoftsoilareascaneffectivelyimprovesoilpropertiesandpreventgeologicaldisasters.Theoptimalconcentrationoffoamstabilizerwasfoundtobe0.3%.Theuseoffoamstabilizercansignificantlyimprovethesoilstrengthandreducegroundsubsidence,