Response of saturation-capillary pressure relationship to the water table fluctuation in a sandy medium
气-水两相砂介质中饱和度-毛细压力关系与水位波动之间的响应

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.