非饱和黄土路基水分场的数值分析

Moisture migration in unsaturated loess subgrade

考虑含水率和密度影响,给出了非饱和黄土路基水分场的计算模型,探讨和确定了模型参数。指出非饱和黄土水体积变化系数m2w并非恒值,不仅随含水率的变化而变化,还明显受到干密度的影响。在含水率相同时,密度变化引起的m2w值的变化在高含水率时比较大,在低含水率时比较小。密度对非饱和黄土渗透系数kw亦有显著影响。进一步考虑参数kw、m2w和水头之间的非线性关系,探讨了时间步长的取值问题。然后,应用编制的有限元程序,模拟不利降雨条件,对黄土路堤入渗过程进行了计算分析。揭示出黄土路基湿软区随时间的增大过程,湿软区域大小受到土体密实度的显著影响,密度较小路基湿软区域大小明显大于密实度较大的路基。比较大的湿软区域易导致路基路面病害。增加路基土体密实度,对防止雨水入渗危害也是有利的。

Taking the soil density and water content into account, a numerical model of moisture migration in unsaturated loess subgrade was given, and parameters of the model were obtained. It was put forward that the coefficient of water volume change m^w2 was not only related to moisture content, but also to soil density. The change of m2^w resulted from density change was large in loess with more moisture content, and is was small in that with less moisture content. Coefficient of permeability kw was also related to the loess density. Based on analysis of nonlinear relationship between kw, m2 and water potential, time interval was got. Furthermore, by simulating unfavorable rainfall, moisture migration in loess subgrade was studied. The slaking scope in subgrade by seepage was gradually enlarged. The slaked area was related to the loess density, small density of subgrade loess resulted in large slaking scope. Eonstructing subgrade in loess with large density was advantageous to avoid seepage damage.