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污染控制技术及原理

Response of saturation-capillary pressure relationship to the water table fluctuation in a sandy medium

基金项目：广东省自然科学基金(No.8151027501000008);河海大学水文水资源与水利工程科学国家重点实验室开放基金(No.2007490511);中山大学后备重点课题

摘要：利用时域反射仪(TDR)与微型张力计(T5)联用装置,测定气-水两相砂介质中因水位波动产生的连续干燥与湿润循环过程中饱和度-毛细压力(S-p)关系曲线.同时,研究了多重水位波动对S-p关系曲线、孔隙流体运移的滞后性及空气剩余饱和度的作用.结果表明,TDR、T5和数据自动采集器联用装置可较准确测量出气-水两相条件下S-p关系的动态变化.同一介质中不同干燥过程的侵入压值比较接近,与干燥过程的初始水饱和度无关;而干燥或湿润过程的S-p关系曲线和滞后程度则与其初始水饱和度密切相关.在特定的干燥和湿润循环过程中,初始水饱和度大小对空气剩余饱和度的值影响不大,用于预测非湿润相流体剩余饱和度的Land的假设需要修正.本研究结果对进一步研究水位波动条件下地下有机污染物运移具有借鉴作用,可为修正NAPLSimulator提供实验依据.

Abstract：A reliable setup for measuring water saturation and capillary pressure was used to obtain saturation-pressure(S-p)relationships of air-water two-phase sandy medium in consecutive cycles of drainage and imbibition resulting from water table fluctuation.The setup,composed of a TDR,T5 tensiometer and datataker,could accurately measure the dynamic S-p relationships in air-water two-phase sandy medium.The effects of consecutive water table fluctuation on the S-p relationship,hysteresis and residual air saturation were investigated.The entry pressure was not dependent on the initial water saturation in a drainage process,and all the entry pressures of different drainage processes in the sandy medium approached a constant value.However,both the S-p relationship and the hysteresis were dependent on the initial water saturation in drainage or imbibition processes.In our tests,residual air saturation was not dependent on the initial water saturation under specific cycles of drainage and imbibition.Modifications to the generally-accepted Land model are needed to estimate a non-wetting fluid's residual saturation.The research will contribute to both further study on the migration of LNAPLs in the subsurface under water table fluctuation,and the modifications of NAPL simulator with experimental data.

Key words：water table fluctuation drainage imbibition saturation-capillary pressure relationship hysteresis