非饱和土渗透系数的一种测量方法和预测公式

Direct measurement method and prediction formula for permeability coefficient of unsaturated soils

总结了非饱和土渗透系数的各种测量方法和预测模型。在此基础上,提出一种直接测量瞬态渗透系数的方法和预测模型。这一测量方法采用多步溢出法测量土水特征曲线,同时实时测量渗透流量和土样的含水率。在试验过程中,把气压强增量分为两个部分:一部分克服渗透阻力,驱赶水分运动,另一部分平衡静水平衡条件下的表面张力,转化为基质势,从而根据达西定律公式求出瞬态渗透系数。另一方面,利用孔隙水的平衡微分方程,引进雷诺层流理论来解释土体渗透产生的土骨架和孔隙水之间的相互作用力,推导出了非饱和土渗透系数的理论公式,该公式只有一个参数,可以通过讨论不同孔隙率、饱和渗透系数与土水作用力系数之间的关系拟合得到,从而预测出非饱和土渗透系数。通过与试验结果的对比,证实了所提出的测量方法和预测模型的正确性。

Various measurement methods and prediction models for the permeability coefficient of unsaturated soils are summarized.A method for measuring the permeability coefficient and a prediction model are proposed.This measurement method,based on the multistep outflow method,can measure the soil-water characteristic curve and the water content of the soil samples in real time.In this method,the increment of gas pressure potential is divided into two parts:one part overcomes the osmotic resistance and drives pore water,the other balances the surface tension of hydrostatic equilibrium conditions and converts it into matrix potential,then,the permeability coefficient can be obtained by the Darcy’s law.On the other hand,the predicted model is derived based on the equilibrium equation of the water phase.Only one parameter is required,and this parameter can be more easily obtained by using the permeability tests on saturated soils with different porosity values.A number of test results in the literatures are employed to validate the proposed measurement method and predicted model,and they indicates good agreement with the experimental data.