降雨是滑坡失稳的常见诱发因素之一，现有数值模拟方法由于不能考虑来自基岩边坡的径流对滑体渗流的补给而低估了真实的降雨入渗水量，导致在评价降雨对滑坡稳定性特别是深层滑动影响时存在一定不足。以Richards方程和有限元法为基础，忽略降雨对渗透性极低的滑床和滑带的影响，将滑坡渗流计算域缩小为滑体，以避免因滑体与滑床（滑带）渗透性差异巨大引起的数值计算困难；依据基岩边坡水平长度和滑体降雨入渗边界饱和情况，修正降雨入渗边界，实现了考虑径流补给的滑坡降雨入渗简化数值模拟。算例表明，该方法所得渗流场更加符合实际情况。以三峡库区某滑坡为例，模拟了2006年10月～2009年12月间滑坡在库水升降和降雨条件下的渗流场和安全系数的演化过程；计算结果表明，考虑径流补给时滑坡后部的渗流场饱和区域明显较大，稳定系数降低较多，与位移监测资料显示的佐证较为吻合；若不考虑径流补给，则降雨对滑坡稳定性影响不大。

Rainfall is one of the most critical factors that results in the landslide instability. However, the influence of runoff from bedrock slope on infiltration has not been considered by the existing numerical methods so that unfavorable infiltration is underestimated and the stability of landslide, especially those deep slides, is overestimated. In this paper, based on Richards’s equation and FEM, a 2D simplified numerical method is proposed, which can consider the influence of runoff supply on the infiltration of sliding mass. In the proposed method, calculation domain only contains sliding mass in order to avoid the numerical problems induced by the large difference between the permeability coefficients of landslide body and landslide bed (or slide zone), and rainfall boundaries are corrected according to the horizontal length of bedrock slope and saturation of slope surface. The seepage field and stability of an existing landslide in the Three Gorges Reservoir Area are simulated under the water level fluctuation of reservoir and the rainfall from Oct., 2006 to Dec., 2009. It is shown that the saturated zone in the trailing edge of landslide becomes significantly enlarged when the runoff supply is considered, and thus the stability decreases more significantly, which is consistent with the data from the displacement monitoring. In addition, rainfall trivially influences the stability of landslide if the runoff supply is not taken into account.