基坑降水引起的相邻建筑物直接经济损失预测研究(Englis

DirectlossPredictiononBuildingsaroundConstructionPitCausedbyGroundWaterPumpingSONGJianxueZhengzhouUniversity1incollaborationwithSONGDanjuoutline•Background•Groundwatertableafterpumping•Groundsettlementcausedbywaterpumping•Groundsettlementandsettlementgradient•Adjacentbuildingdirectlossprediction•Practicalapplication21Studybackground●Moreandmoreskyscrapers:deepfoundationpits●moreandmoreundergroundprojectsMetroundergroundshopmallResultin:Deepexcavation3ZhengzhouInternationalConferenceandExhibitionCenter(ICEC)4ZhengzhouICECHotel5ZijingshanMetroStation:Inthefuture,theL-2Metrolinewillrunbeneaththisstation.Herewillbeabusytransfercenterfortravelers.6Adjacentgroundsettlementandcrackcausedbygroundwaterpumpinginconstructionpit7Pipelinecutbygroundsettlementthatresultedfromgroundwaterpumping8Residentialbuildingsdamagedbygroundsettlementthatresultedfromgroundwaterpumping9Howfar?Magnitude?Issettlementmagnitudetheonlyfactor?10ConstructionpitgroundwaterpumpingDeterminingofgroundwatertableandcontourafterpumpingBuildingdirectlossvs.groundsettlementgradientGroundsettlementgradientDeterminingofgroundsettlementandcontourAdjacentbuildingdirectlossprediction112Groundwatertableandcontourafterpumping2.1GeneralalgorithmforwatertabledeterminingA-Solutionoffluidmechanism:strictanalyticsolutionB-Solutionofhydraulics:approximatesolution()()HHHTTWtxxyy2222220HHHxyz(3-Dstableflow)(2-Dstableflow)12C-NumericalsimulationPorewaterpressurenumericalsimulation-113Porewaterpressurenumericalsimulation-214Groundsettlementnumericalsimulation-115Groundsettlementnumericalsimulation-216However,thesealgorithmsaretoocomplicatedtobeappliedinpracticalproject!Ontheotherhand,mostoftheChinesecivilengineersareusedtofollowingthenationalcodessystemThismustbetakenintoconsideration!1718Assumptions:2-dimensionstableflow,withoutwatercuttingwallsurroundingthepitDeterminingofgroundwatertableafterpumpingThegroundwatertablemaybeobtainedbylglg()lglgnwwSRrDSRr19(Dupuit'sequation)20LoessgeologicalareaAlluviongeologicalarea21Beforeapplying,thevalidityoftheformulahastobecheckedSixprojectsarechosenascasesstudy,andonlyoneisdiscussedhereZhengzhouMetroStation:AthleteCenterStation222324locationSW-70SW-67SW-68SW-69monitoredwatertable(m)-10.62-11.47-12.02-10.8Calculatedwatertable(m)-10.95-9.69-9.69-8.74Distancetotheedgeofpit(m)-26-40-40-52Calculatedwatertableandmonitoredwatertable2526CalculatedwatertableandmonitoredwatertableAfterverificationinsixprojects,itisfoundthattheDupuit'sequationcanbeusedtodeterminethewatertableafterpumping3.1Algorithm-soilcompressionaccumulation(SCA)Fortheconvenienceofengineers,thealgorithmstipulatedinChineseNationalCode(SCA)isemployed:22111()2nwiiisisHHE2()mwnjjijnsiHsHHE3Groundsettlementcausedbywaterpumping272211()2nwiiisisHHES2-usuallyverysmall,maybeneglectedAccordingtotheNationalCode,inordertoobtainedS1,themodificationfactorψhastobedeterminedfirst28modificationfactorψ:_determinedbylocalengineeringgeologycondition.(3.1)No.WatertableCalculatedsettlement(mm)Monitoredsettlement(mm)ψ110.7991.3527.00.2956210.4389.0324.90.2797312.16100.8733.60.3331413.8411433.80.2965515.15125.635.50.2826614.52119.9429.70.2476714.76122.1234.80.2850814.62120.8336.30.3004915.14125.5137.50.2988Modificationfactor29modificationfactorψ30Presumeψcomplywiththestandardnormaldistribution22()21()2upe0.29310.2910.021，0.0217.2%10%0.291CVTakeψas0.29,thenthesettlementcalculationerrorNo.Modifiedcalculationsettlement(mm)S=ψS1Monitoredsettlement(mm)error126.49271.88%225.8224.93.69%329.2533.62.94%433.0633.82.19%536.4235.52.60%634.7829.71.71%735.4134.81.77%835.0436.33.47%936.4037.52.94%324Buildinglossresultsfromgroundsettlement4.1MainassumptionOnlydirectlossistakenintoconsideration33344.2Algorithm(1)Thegroundneartheconstructionpitisdividedintoaseriesofdonuts.(2)Equation(3.1)isemployedtodeterminethesettlementofeachdonut(themiddlelineofeachdonutistakenastarget).(3)Settlementgradientbetweenbordereddonutsisobtained.(4)Economiclossratevs.groundsettlementgradientissetup.(5)Acertainscopearoundthepitischosen,allbuildingslossinthescopeisaccumulated.354.3Donuts4.3.1Usually,thegeometriccenterofpitissetasthecenterofalldonuts4.3.2Theaffectingscope(takenas5Sw,Sw-thedepthofwatertablefallingbeneaththepitground)isdividedintoaseriesofdonutswiththeincrementas0.2Sw364.4groundsettlementgradient11iiiiiSSGDDNo.G1G2G3G4G5G6G7G8Gi0.320.3.0.270.250.230.220.200.19No.G9G10G11G12G13G14G15G16Gi0.180.170.210.220.200.190.180.17No.G17G18G19G20G21G22G23G24Gi0.160.150.140.220.240.250.220.1837GroundsettlementgradientintheCaseProject38Generally,thefurtherthedistancefromthepitedgeis,thesmallerthegroundsettlementgradientis.39However,ifadonutrunsacrossoverthesoilsurfacewhichisbelowandabovethewatertablebeforeandafterpumping,thegradienthereislikelytoleapsignificantly.40Forthesakeofsecurity,1‰istakenasthethresholdofgroundsettlementgradient.4.5Thethresholdofdifferencesettlementbuilding414.6Therelationshipbetweengroundsettlementgradient(G)andeconomiclossrate(λ)ofbuil