非饱和土壤渗透方程的简化差分计算

A Simplified Difference Method for Infiltration Equation in Unsaturated Soil

在对理查兹（L．A．Richards）渗透方程提出的近似精确解基础上，研究了菲利普（J．R．Philip）以粘土为例的渗透速度计算公式，并对非饱和土壤中长时间渗透时出现的误差及原解的缺陷加以修正，提出了更简捷合理的无时间差分变量计算模型。给出了渗透速度随时间的过程线、渗透深度与土壤湿度的变化曲线。该方法经过大量验证，可以得出结论，它对砂土、壤土中的渗流也适用。与常用的时间差分方法比较，该法得出的土壤渗透湿度深度曲线是正确的，且计算时间显著减少，消除了时间迭代误差。

In this paper, we discussed Philip,s quasi analytical solution for Richards, infiltration equation． We modified the solution and corrected the errors of time variant for unsaturated soil infiltration in the solution． The example chosen for calculation is that of infiltration into a vertical semi－infinite column of Yolo Light Clay． We presented its function of infiltration velocity and its moisture profiles during infiltration． This method is also suitable for the infiltration cases in sand and silt loam． The results of calculation illustrated that the method has a great advantage of the finite difference method in the aspect of calculation speed．