地下非均匀-非饱和带中开挖洞室的渗流数值模拟ppt

地下非均匀－非饱和带中开挖洞室的渗流数值模拟

－以美国核废物处置场渗流评价为例地下水数值模拟的现状对比美国：社会经济环境稳定期

主要以水资源的管理与开发调等。局部污染的治理为目标。例如：湿地的恢复，加油站污染的清理，以及废物处置场址评价等。勘探布局：资本经济控制主要的商业软件：MODFLOW，TOUGH2，MT3D，FEFLOW各单位自主开发的专项软件模式：（老问题＋老模拟手段） 新问题＋新模拟手段国内：经济大发展、社会快速城市化及生态环境大变化？？？勘探布局：？？？？模式：老问题＋新模拟手段地下水模型面临的主要问题:介质非均质地下水中的污染物运用移是一个复杂的地质过程，也就是说我们不能够直接观察到地下水在哪儿流，水中的污染物以多快的速度运移，以及污染物浓度的变化。而实际上，人们在开开始的时候仅仅知道可能的污染源(例如垃圾场，工业废水排放点，农药或化肥的面上污染等等)和在井水，泉水或观测井中检测出的污染物。地下水模型面临的主要问题:实测数据的代表性水文地质参数的尺度效应现场试验结果的客观解释数值模拟结果的可靠性

数值模型预测的可操作性探索、途径。。。长期以来，人们只能根据有限的地质和水文地质勘探资料来分析和研究含水层，并发现通过不同的钻孔或抽水试验得到不同的参数，即含水介质的参数具有不确定性。随着地下水流动与溶质运移模型的不断发展，人们对含水介质参数的不确定性问题日益重视，并一直在寻求各种能够更合理描述含水介质参数分布的理论与方法。模拟结果的可信度概念模型不正确＋模型手段不合适→结果没法信概念模型正确＋模型手段不合适→结果不可信概念模型不正确＋模型手段合适→结果不可信概念模型正确＋模型手段合适→结果可信概念模型基本正确＋模型手段较合适→结果基本可信ModelingandAnalysisofSeepageintoDriftsinYuccaMountainProposedNuclearWasteRepositorySiteatYuccaMountain,NVGuominLiEarthSciencesDivisionLawrenceBerkeleyNationalLaboratoryYuccaMountainSite-ScaleGeology:--AnimportantissueforthelongtermperformanceoftheproposednuclearwasterepositoryatYuccaMountain:CorrosionratesofwastepackagesWastemobilizationratesTransportratesofradionuclidesleavingthedriftSeepageofWaterintoaDriftFieldInvestigationandTestsFieldsurveyandtestsprovidedalotofinformationaboutgeologicbackgroundandhydraulicparameters:DetailedlinesurveyoffracturesalongtheExploratoryStudiesFacility(ESF)maindriftSingleHeaterTest(SHT)DriftScaleNicheSeepageTestsExploratoryStudiesFacility(ESF):8kmlong,8mdiametertunnelwithnichesandalcovesfortesting;EnhancedCharacterizationRepositoryBlock(ECRB)crossdrift:2.7kmlong,5mdiameter.

ResearchFacilitiesatYuccaMountain,NVDetailedLineSurveyofFracturesAlongtheESFMainDriftDetailedLineSurveyofFracturesalongtheESFPresenceoflongfracturesamongmanyshortfracturesSuggestamediumwithadensenetworkofshortfractures(approximately1-4m)(Sonnenthaletal,1997)Thespacingisconsistentlylessthanfracturelengthsforallthefracturegroupings(LiandTsang,2000)SingleHeaterTestDriftScaleSingleHeaterTestAreaFracturesarewellconnectedDistributionofpermeabilityoffracturecontinuum(TsangandCook,1997)NicheStudiesConceptualModelofSeepageModelforPAStochasticFractureContinuumModel:toaccountfortheheterogeneityofflowfieldinthefracturedformationFracturepermeabilityisseveralordersofmagnitudehigherthanthematrixpermeabilityThepercolationfluxthroughtheTSwunitoccurspredominantlyinthefracturesTheTSwunitcomprisesawell-connectedfracturenetworkonascalemuchsmallerthanthedriftradiusFieldtestsshowthatthebehaviorofthefracturenetworkequivalentlytoacontinuum,heterogeneousmediumwithconsiderablevariationinpermeabilitySeepageModelforPerformanceAssessment(PA)isconsistedwiththeSeepageCalibrationModelUnsaturatedsteady-stateflowscenarios:asinglecontinuumstochasticmodelofthefractureflowMatriximbibitions:insignificantforalongtermseepagemodelingwhennear-steadylate-timedataarenolongeraffectedbyitAirpermeability:representativeofthehydraulicconductivityoftheexcavation-disturbedzonearoundthedriftCharacteristiccurves:relativepermeabilityandcapillarypressurearecontinuousfunctionsofeffectiveliquidsaturationfollowingthevanGenuchten-MualemmodelEvaporation:suggestingaveryminorinfluenceonseepageratesinnichetestsPercolationflux

NumericalModelConcernedwithblockaroundthedriftof5.5mdiameterGenerate3DmeshandcutoffadriftMappingheterogeneouspermeabilitytothe3DmeshBoundaryconditions:topboundary–representingapercolationfluxarrivingthedriftmodelarea;bottomboundary–withfreedrainagecondition;foursides–no-flowboundariesCode:TOUGH2–TransportofUnsaturatedGroundwaterandHeatModelVerificationHeterogeneousversusHomogeneousModelSensitivityAnalysispercolationfluxpermeabilityvanGenuchtenparametersstandarddeviationcorrelationlengthPredictiveSimulationsforPerformanceAssessment(PA)Widerangeofparameters Percolationflux:1to1000mm/yr Meanpermeability(Log10base):-9.5to-14.5 1/alpha:100to1000Pa othersRunsonworkstationswithparallelmethod:21600 1080casesforonerealization20realizations3Dresultsforasingerun: Saturationprofiles Driftwallseepagelocations SeepageratesConcludingremarks(1)

Byreviewingavailableinformationfromthefieldinvestigationandtests,conceptualmodelwasbuiltandcontinuumheterogeneouspermeabilityfieldsweregeneratedThenumericalapproachwasverifiedagainsttheanalyticalsolutionofPhilipetal.(1989),andgoodagreementwasobtainedSensitivityanalysisofseepageinheterogeneouscontinuumshown:seepageiscalculatedtobelargerforsmallermeanpermeability,smallervanGenuchtenparameter(1/alpha),largerstandarddeviationinlnk,largerspatialcorrelationlength,andlargerpercolationfluxConcludingremarks(2)Heterogeneityiscriticalforseepagecalculations:flowchanneling/flowfocus,localpondingUncertaintyassociatedwithgeostatisticswasevaluatedthroughsimulationsofmultip