ConstructionStatementforPVC真空预压发处理软土地基施工方案模板

ConstructionStatementforPVC真空预压发处理软土地基施工方案资料内容仅供参考，如有不当或者侵权，请联系本人改正或者删除。ProposedDesignPhilosophy,Construction,InstallationandMonitoringMethod(asper22.1.7ofsection1.0)SourceofborrowspitindicatingthelocationandquantityWehavelicensegivenbyVietnamauthoritytoexploitaquantityof8,400,000m3inNhaBeriverandthelocationisinNhonTrachdistrict,DongNaiprovince.PhysicalproprietiesofproposedfillmaterialThesamplingtestofsandproposedtouseiscarriedoutaccordingtoAASHTOM45-89,C144-88(seeTestResultofAnalysesofSandcomponent).Thespecificweightofthesandis2.634,unitweight1.5g/cm3,organiccontent2.87%andmodules2.52.3.Proposedmethodofstatementandmonitoringdevices3.1MethodstatementAccordingtothegeotechnicalreportofthesite,thevoidratioofthesoftsiltyclay(e)is2.377,andthepermeabilitycoefficient(Kv)5.5*10-7cm/s.Ifweadopt”wickdrainsandpre-loading”methodtoreachasoilbearingcapacityof50Kpa,75Kpa,100Kpaunderthesite’sconditions,theconsolidationperiodwouldbefarbeyondtheproposedworkperiod.Forthepurposeofreducingtheconsolidationperiodoffoundationsoilanoverloadshouldbeadded,thoughtheloadingwouldbe7.30mhightofulfillthebearingcapacityof100Kpa.Obviously,thistechniquewouldbearatremendousnumberofloadingandunloading,whichwouldalsomeanahighconstructioncost.Thestabilityofsideslopewouldalsobedifficulttomonitor.BasedonourpreviousexperienceofsoftsoilimprovementofChinacoastalandHiepPhuocPowerPlantinNhaBe,15kmSoutheastofHochiminhCity,thepre-loadingmethodisappropriateonlyforgeneralarea.Inprocessareawesuggesttoadoptedthefollowingmethod(detailsseedrawings”ProposedProcessAreaPlan”and”ProposedProcessAreaZone”inpage6,7):f=50Kpa,vacuumprecompressionmethod;f=75Kpa,vacuumprecompressionandfillingwater(2.0m)onmembranemethod;f=100Kpa,vacuumprecompressioncompoundwithloadingmethod.Thehydraulicfillingofseasandshouldbeadoptedundertheelevation+2.80,whichisspecifiedinthetenderdocuments.Butbasedonoursiteinvestigationreport,weproposetousesweetwatersandinsteadofseasandforthesefollowingreasons:Finegradeandhighmudcontentoftheseasand;Nolocalfacilitiesavailablesuchashydraulicfillingmudabsorption.Thebackfillmaterial(sweetwatersand)willbedeliveredbybargestothenearestdockandthencarriedbytruckstothesite.3.2MonitoringdevicesAccordingtotherequirementofthetenderdocuments,settlementgaugeshouldbeinstalledat50mx50mgridandbemeasuredbylevelinginstruments.Inaccordancewiththerequirementoftheowner,thestaticpenetrationtestshouldbecarriedoutatthe10specifiedpointsandthepenetrationinstrumentsshouldbeburiedthroughthewholedepthofthecompressiblesoillayers.Thecompactiontestoffillingmaterialsinsiteshouldbecarriedoutwithheavycompactor.DesignphilosophytoachievetherequirementofthespecificationforsoilimprovementphilosophyofvacuumprecompressionmethodThevacuumprecompressionmethodisusedtoconsolidatefoundationsoil.Thismethodconsistsinlayingonthesurfaceoffoundationsoilasandbed,andininstallingadrainagesystemwithwickdrains.Thesandbeddrainlineisburiedandconnectedwithvacuumsystemtoformanairexhaustandadewateringsystem.Asetofairtightsealmembranesislaidonthesurfaceofthesandbedwithitsedgeburiedinsoil.Thus,anegativepressureareawithinsandbedandfoundationsoilcanbeformedfromairexhaustanddewaturingpumps.Thevacuummethodcanreachasoilbearingcapacityof80KPa.Underthevacuumcondition,soilisinthestateofconsolidatingandporewaterisdischargedfromsoilunderthepressuredifference.Theconsolidationiscompletedwhenpressureofsoiltobeconsolidatedisreachingthesamepressureofthedrainagesystem.Thephilosophyofvacuumrecompressionmethodisthatunderthepressuredifference(Pa-Pv),soilcanbeconsolidated;PaindicatesatmosphericpressureandPvindicatesairpressureinthesandbedandtheverticaldrains.Inthecalculationofconsolidationofthefoundationsoil,theRENDULIC-TERZAGETheoryandBICOTTheoryofConsolidationcanbeadoptedwhicharethesameofthoseadoptedinloadingrecompressionmethod.Thedropofthegroundwatertablemayalsoacceleratetheconsolidationoffoundationsoilbesidethepressuredifference.Theeffectivestressinthesoilincreasessuccessivelyduringtheperiodofconsolidationofthefoundationsoilwithvacuumrecompressionmethod.Thehorizontaldisplacementofthesoilistowardthecenteroftheconsolidationareafromthebeginningoftheperiodofvacuumrecompression,whichisdifferentfromtheloadingrecompressionmethod.Sothestabilityofthefoundationsoilwillnotbecomeaproblem,andtherequiredvacuumcapacitycanimmediatelybeobtainedandconsequently,theperiodofvacuumrecompressioncanbecurtailed.Detailsisshownindrawings”DesignPhilosophyforVacuumPrecompression”and”FlowDiagramofVacuumPrecompressionMethod”inpage8,9.Regardingtheshortworkperiodofthisproject,thevacuumcompoundwithloadingrecompressionmethodisusedintheprocessareawheretherequiredbearingcapacityofthefoundationsoilis100Kpa.Ithasbeenprovedfromthetheoreticalcalculationandourpreviousexperiencethattheeffectsofvacuumandloadingrecompressionmethodsontheconsolidationcanbecoaxed.Forthispurpose,asoilcapacityof150KpahadbeenobtainedinoneofourpreviousprojectintheturbinehouseofHiepPhuocpowerplantlocatedatNhaBedistrictinHochiminhcity.Duringthevacuumprocessandunderthepressuredifference(Pa–Pv),theporewaterpermeatesintotheverticaldrainsandtheconsolidationoccurs.Ontheotherhand,whenusingpre-loadingmethod,theairpressureraisestoPpandtheconsolidationoccursunderthepressuredifference(Pp–Pa).Therefore,byusingthevacuumcompoundwithpre-loadingmethod,thepressurecanbeincreasedto(Pp–PV)andtheconsolidationeffectwouldbeimprovedasaresult.Theprocessofvacuumcompoundwithpre-loadingmethodisshownindrawing”TheProcessdrawingofVacuumPrecompressioncombinedwithLoadingMethod”inpage10.4.2MonitoringmethodTheloadingheightandloadingperiodofeachstepofgeneralareaismainlycontrolledbythestabilityofthefoundationsoil.Thesettlementmonitoringshouldbemainlyconcernedinthisarea.Becausethevacuumprecompressionmethodwillnotcauseasoilstabilityproblem,thesitemeasurementshavelesssignificancecomparabletopre-loadingmethod.Accordingtotherequirementofthetenderdocuments,settlementgaugesshouldbeinstalledat50mx50mgridandbemeasuredbylevelinginstruments.Thetotalsettlementandsettlementspeedofthefoundationintheloadingareaaswellasthesettlementortherisingheightinthesurroundedareamustbemonitored.ThefinalsettlementScanbecalculatedfromthesitemonitoringdata.TheconsolidationsettlementScandtheaverageconsolidationratioareobtainedfromthisvalue.Moreover,thevaluecanalsobecalculatedaswellastheaverageconsolidationcoefficientCv.Accordingtotherequirementoftheowner,thestaticpenetrationtestshouldbecarriedoutatthe10specifiedpointsandthepenetrationinstrumentsshouldbeburiedthroughthewholedepthofthecompressiblesoillayers.4.3PreliminarygeotechnicaldesignforverticaldrainsandsoildischargeThetypeSPBplasticdrainageplateisadoptedastheverticaldrainsinthisproject.Theverticaldrainswouldbedistributedaccordinglytoanequilateraltrianglepattern.BasedonourpreviousexperiencesofsoftsoilimprovementintheMekongdeltaareaandaccordingtotheworkrequirementsfromtheproject,webelievethatthebearingcapacityofprocessedfoundationsoilcanbereached.However,itisarduoustoreachthesamerequirementforthedeformation.Itneedsacomparativelylongperiodtoattainastablestateoffoundationsoilsettlement.Inaccordancewiththetenderdocumentforthegeneralarea,thefillingmaterialshavetobewellcompactedtomeetthebuildingstandard.Still,therearenorelevantrequirementsofbearingcapacity,sotheinsertingdepthoftheverticaldrainsshouldbelessthanthethicknessofthesoftsoillayerstoavoidtheoccurrenceofextremesettlement.Intheoppositecase,thatwouldimplyalargeadditionalquantityofloadingmaterialsandasoaringconstructioncost.Combiningvacuumtechniquewithloadingmethod,thedifferentrequirementsofbearingcapacityofprocessareacanbefirmlymet.Obviously,theairtightconditionduringvacuumprecompressionisacriticalfactortoensureasufficientvacuumlevel.Thedepthofverticaldrainsintheprocessareaisestimatedtobe10mtoensurethattheendofverticaldrainsiswithinthesoftsoillayerwhichisabout14mdepth.Thiswillavoidanyleakagefromlowersandlayer.Theintervaloftheverticaldrainsingeneralarea:L=1.20mForprocessarea:f=5t/m2,L=1.2m.f=7.5t/m2,L=1.1m.f=10t/m2,L=0.7m.Theinitialgeotechnicaldesignisshownintwotables:”GeotechnicalDesignofVacuumPrecompressionMethodofProcessArea”and”GeotechnicalDesignofPre-loadingMethodofGeneralArea”inpage11,12.ProposedverticaldrainsmaterialsTheSPB0-IItypeverticaldrainisadoptedfromCHINA.TheproprietiesoftheproductionmeettherequirementsofChinesestandardDB3201Q18-87(detailsisshownbelowintable”QualityStandardofSPBVerticalDrains”).ualityStandardofSPBVerticalDrainsParameterUnitTypeRemarksSPB-1SPB-2SPB-3MaterialsPlasticstripcorecoatedwithamembranefilterSectiondimensionsWidthmm100210021002Thicknessmm3.54.04.5Longitudinaldraincapacitym3/s15*10-625*10-6Sidepressure350KN/m2TensionstrengthKN/10cm>1.0>1.3Elongationis100%Elongation<10<10Permeabilitycoefficientcm/s5*10-45*10-4Capacityofinsulatingsoilm<75<75TensionstrengthofmembraneDryN/cm>15>30Elongationis10%WetN/cm>10>20Elongationis15%Linearweightg/m90-10090-100Unitlengthm200200SiteclearingSiteclearingGeotextilelayingPreparationofwickdrainsinsertingequipmentSiteofficeandcontrolcenterVacuumpipesinstallWickdrainsinsertionSecondsandbeddingFirstsandbeddingMembranelayingAirextractingequipmentVacuumgaugeandrelayinstallAirextractiontestPrecompressionbyairextractionVacuumpressureandsettlementreadingsintheprocessareaEquipmentremovaloftheprecompressionmethodRefillandlevelingWeirconstruc-tionControlandoperationcenterElectricalandlightcircuitRecheckthevacuumpumpsTemporarywaterpumpsinstallationVacuumpipepreparationMembranepreparationSettlementgaugesInitialreadingofsettlementandrelayResiliencereadingofgroundsettlementLeakagerepairofmembraneResultsverification FlowDiagramofVacuumPrecompressionMethodGeotechnicaldesignofvacuumprecompressionmethodsofprocessareaProcessArea(m2)Averagedepthofsoftsoil(m)BearingCapacityoffoundationsoil(t/m2)Intervalofverticaldrains(m)Depthofverticaldrains(m)CalculatedFinalconsolida-tionsettlement(m)Depthofverticaldrains(m)CalculatedFinalconsolida-tionsettlement(m)EstimatedSettlement(m)Depthofverticaldrains(m)CalculatedFinalconsolida-tionsettlement(m)128254*__________2528614.4210.02.101.608.01.62.9510.02.301.808.01.90100.813.43.6010.02.692.408.02.35241428.00*____________37450.0013.3910.02.101.608.01.62.7210.02.301.808.01.90100.812.33.3010.02.692.408.02.15354313.00*____________49603.0013.0551.0212.02.5310.02.101.608.01.62.6510.02.301.808.01.90100.812.03.2310.02.692.408.02.15Note:The”*”showsthatthenumeratormeanstheproposedprocessarea,whichisextendedfromtheareaspecifiedinthetenderdocuments(denominator)byextendingedgeto4.0m.Whenf=7.5t/m2,thesettlement(1.8)iscalculatedbyusingtheaveragesettlementaftervacuumprecompressionofthemainbuildingofHiepPhoucpowerplant(1.55)addedsettlementoccurredinconsolidationperiod(90days)whichis(90*3)mm.

GeotechnicaldesignofvacuumprecompressionmethodinprocessareaSchemeProcessArea(m2)Averagedepthofsoftsoil(m)BearingCapacityoffoundationsoil(t/m2)Intervalofverticaldrains(m)TreatmentDepth(m)EstimatedSettlement(m)128254*_______________2528614.4151.210.01.60