考虑任意初始条件的均质土质覆盖层降雨入渗解析解

均质土质覆盖层作为填埋场与大气环境的隔离结构其主要功能是控制雨水入渗,近些年该类覆盖层在北美一些干旱和半干旱地区被证明是有效的。基于二维非饱和土渗流控制方程,采用可考虑土体进气值的指数函数描述土体的土水特征曲线和渗透系数曲线,使用单位梯度边界作为土质覆盖层的底部边界条件,推导出可考虑任意初始条件的降雨入渗移解析解。通过与前人试验结果比较与分析,证明了该解析解的有效性。对比分析了均质土质覆盖层底部分别取单位梯度边界、渗流审查边界和固定孔压边界对降雨入渗及渗漏量的影响,分析结果表明:与渗流审查边界和固定孔压边界相比,单位梯度边界更适合土质覆盖层的渗漏量计算。利用该解析解分析不同初始条件对累计渗漏量的影响,结果表明覆盖层累计渗漏量随其底部初始体积含水率的增加而增大。为土质覆盖层防渗漏性能评价提供了一种简单实用的计算方法。

Analytical solutions for rainfall infiltration into monolithic covers considering arbitrary initial conditions

As an isolation barrier between landfill and atmospheric environment, monolithic covers are used to control rain water infiltration and deep percolation into landfill. In recent years, the covers are proved to be effective in some arid and semi-arid areas in North America. An analytical solution for rain water infiltration into a monolithic cover is presented on the basis of the two-dimensional governing equation for unsaturated flows. The analytical solution can take arbitrary initial conditions into consideration. To obtain the analytical solution, it is assumed that both the soil-water characteristic curve and the permeability function can be described by using the exponential functions considering entry air value and the bottom boundary of the monolithic cover is set as the unit gradient boundary. The analytical results are compared with those measured results reported in literatures, indicating that the analytical solution is effective. The influence on rain water infiltration into a monolithic cover and its percolation of using three boundaries including unit gradient boundary, seepage face boundary and fixed pore water pressure boundary as its bottom boundary are analyzed. The results indicate that compared with the other two boundaries, the unit gradient boundary is more suitable for the monolithic covers to calculate the percolation. The influence of various initial conditions on accumulated percolation of monolithic covers is analyzed using the analytical solution. The research indicates that the accumulated percolation increases with the increase of the initial volumetric water content near the bottom of the covers. This study provides a simple and practical method for evaluating the performance of monolithic covers to control rain water percolation through a soil cover.