基于不同渗透持时的非饱和黄土渗透系数预测分析

Prediction of coefficient of permeability of unsaturated loess with different seepage durations

首先通过渗透试验和压力板仪试验获得不同渗透持时的黄土的土水特征曲线,在此基础上利用van Genuchten模型对土水特征曲线进行拟合,最后利用拟合参数结合van Genuchten渗透模型进行不同渗透持时的非饱和黄土渗透系数预测分析。研究发现,随着渗透持时的增加,非饱和黄土的渗透系数一直在减小,减小幅度超过50%。渗透持时相同的条件下,非饱和黄土渗透系数随着体积含水率的增加而增加,且在接近饱和状态时,增加的幅度开始减缓。结合扫描电镜试验结果发现,黄土渗透系数减小的重要原因系由于随着渗透持时的增加,黄土中大孔隙减少而中小孔隙增加造成。

The coefficient of permeability of unsaturated loess is very important to seepage calculation and slope instability analysis of loess. Using the direct method to test the coefficient of permeability of unsaturated loess is time-consuming and more expensive. Now scholars prefer to obtain the unsaturated coefficient of permeability through calculation from the soil water characteristic curve(SWCC). Firstly, the saturated coefficient of permeability is obtained through the permeability tests and the SWCC by pressure plate apparatus tests. Then van Genuchten model is chosen to calculate the unsaturated coefficient of permeability by the SWCC. The results show that the coefficient of permeability of unsaturated loess becomes higher with the increase of the volumetric water content and the decrease of the matric suction. The decrease of coefficient of permeability is more 50%. In order to understand the change of unsaturated coefficient of permeability of loess, SEM tests are conducted by JSM-6701 F. From the SEM of loess, it is clear that the large pores become to decrease and the small and medium pores become to increase with the time.