确定渗析平衡时间的数值模拟方法

Numerical simulation of determination of equilibrium time for osmotic technique

渗析法是一种测量非饱和土基质吸力的重要方法,而测量结果是否准确,控制渗析的时间非常重要。基于有限元数值分析软件SEEP/W,建立渗析法的数值模型,分析渗析的试验过程,研究溶液吸力、土样水力参数、初始重力含水率、初始干密度以及土样大小等因素对吸湿条件下非饱和黏土渗析平衡时间的影响。结果表明,随着渗析时间的增加,土样与溶液之间的吸力差逐渐变小,渗析过程变慢;试验用土样不宜过大,对于较小土样,多数条件下土样的渗析平衡时间约为1.5~8.0 d;当溶液吸力较大或土体饱和渗透系数较小时,渗析平衡时间大大增加;渗析平衡时间随土-水特征参数a、n、饱和渗透系数、初始含水率及干密度的增大而减小,随饱和体积含水率的增加而增加。

Osmotic technique is an important method for measuring the matrix suction of unsaturated soil. It is very important to control the osmotic time, which is one of the key points to obtain the accurate measurement result. Based on the finite element numerical analysis software SEEP/W, we set up a numerical model of osmotic technique to analyze water movement during the osmotic process. Then, we analyzed the influences of the suction of solution, the hydraulic properties of soil sample, the initial gravity moisture content, the initial dry density and the size of soil sample on equilibrium time of the osmotic technique for unsaturated clay in the process of humidification. The results show that with the increase of osmotic time, the difference of suction between the solution and the soil sample will decrease and then the osmotic process will become slower. Soil samples should not be too large. For small samples, the equilibrium time for the osmotic technique is about 1.5-8.0 days in most cases. The equilibrium time increases greatly when the suction of solution is high or the saturated hydraulic conductivity of soil sample is low. The equilibrium time decreases with the increase of the fitting parameters（a, n） for soil-water characteristic curve, the saturated hydraulic conductivity, the initial moisture content and the initial dry density. On the contrary, the equilibrium time increases with the increase of saturated volumetric moisture content.