确定滤纸法试验平衡时间的数值模拟

Numerical simulation of filter paper method for confirming equilibrium time

滤纸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,控制滤纸法的试验时间非常重要.基于有限元数值分析软件SEEP/W,建立滤纸法的数值模型,分析滤纸法试验过程中的水分运移过程,研究非饱和黏土的水力参数、初始重力含水率、初始干密度等因素对滤纸法平衡时间的影响.结果表明,试验开始时,干燥滤纸会迅速吸水,随后滤纸与土样吸力才逐渐平衡,以含水率为判断标准得到的平衡时间Tw会小于以吸力为判断标准得到的平衡时间Tψ,建议滤纸法的实际试验时间接近于Tψ.滤纸法的平衡时间约为4~16 d,当土样饱和渗透系数较小时,滤纸法的平衡时间大大增加,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.

Filter paper method is an important method for measuring the matrix suction of unsaturated soil. It＇ s very important to control the testing time which is one of the key points to obtain the accurate measurement result. Based on the finite element numerical analysis software SEEP / W,setting up the numerical model of filter paper method to analyze water transmission process. And take into account the influence of the hydraulic parameters,initial gravity moisture content and initial dry density of soil on equilibrium time of filter paper method for unsaturated clay. The results showthat the dry filter paper will absorb the soil moisture rapidly at the beginning of the test,subsequently,the suction of soil and filter reached balanced state. The equilibrium time judged by moisture content of filter paper（ Tw） is shorter than the equilibrium time judged by suction（ Tψ）. It＇s suggest that the actual test time is close to Tψ. Generally,the equilibrium time of filter paper is about 4- 16 d. The equilibrium time increase greatly for smaller saturated permeability coefficient of soil. The equilibrium time decrease with the increase of the hydraulic parameters（ a,n）,saturated permeability coefficient,the initial moisture content and initial dry density. On the contrary,the equilibrium time increase with the increase of saturated volumetric moisture content.