非饱和砂土坡面降雨非正交入渗试验与数值模拟研究

Tests and numerical simulations of non-orthogonal rainfall infiltration on surfaces of unsaturated sand slopes

传统降雨入渗分析仅以降雨强度在坡面上的正交分量作为边界条件,不符合实际降雨非正交入渗规律。为了研究非饱和砂土的非正交入渗规律性,采用自行研制的室内降雨试验装置对非饱和砂土坡面进行了一系列不同降雨强度、坡角和孔隙比的降雨入渗试验,并对应地进行了正交入渗条件下的数值模拟。测量了入渗率、出渗速率及砂土储水增量随时间变化的关系曲线,分析了雨强、坡角和孔隙比对试验结果的影响。试验结果显示各试验中均无坡面径流现象,与正交入渗边界理论差异显著。通过分析非饱和砂土在传统坡面降雨正交入渗边界条件下的入渗率、出渗速率及砂土储水增量等数值模拟结果与对应的降雨入渗试验结果的差异,证明按正交入渗边界理论计算得到的砂土坡面土体含水率、入渗能力及坡面边界条件转化的判别机制均与实际情况不符。

The traditional rainfaU infiltration boundary, which is determined by decomposing the rainfall intensity simply according to the direction of a slope surface, does not conform to the actual non-orthogonal rainfall infiltration. In order to study the rules of non-orthogonal rainfall infiltration on the surfaces of unsaturated sand slopes, a series of infiltration tests on unsaturated sand slopes under different rainfall intensities, slope angles and void ratios are carried out using a new and self-designed artificial rainfall device. In addition, numerical simulations under the same conditions corresponding to the laboratory tests are employed to analyze the rainfall infiltration. The variations of infiltration rates, seepage rates and water storage increments of sandy soil with respect to infiltration time are obtained, and the influences of the rainfall intensities, slope angles and void ratios on the test results are analyzed. The test results show that the overland flow does not emerge in all the tests. They are different from the orthogonal infiltration theory. Finally, the comparison between numerical simulations and test results unveils the differences in infiltration rates, seepage rates and water storage increments of sandy soil, and demonstrates that the moisture content of the soil slope, water infiltration capacity and the transformation mechanism of boundary conditions, which are calculated with the orthogonal infiltration theory, do not conform to the actual cases of non-orthogonal rainfall infiltration.