根据某水电站河床坝基覆盖层的工程地质特性和水文地质特点，通过现场和室内试验获得水文地质参数，初步判定渗透变形类型。再基于水文地质参数和渗流理论，建立坝基覆盖层的三维数值计算模型，得到渗流场和水力梯度特征，进而分析不同工况下库水通过覆盖层的渗漏量。在此基础上，通过分析不同工况下水力坡降的模拟计算结果，评价了坝基的渗透稳定性问题，与初判的结果进行比对，得出最终结论，为大坝的防渗处理提供合理依据。

 The seepage stability of the overburden layer of a dam foundation is studied in this paper to provide basis for seepage control for the dam. Firstly, according to the geologic and hydrogeologic characteristics of the dam foundation overburden layer, the seepage deformation type is preliminarily estimated based on hydrogeological parameters obtained from site and indoor tests. A 3-D numerical model of the overburden layer is subsequently built to get the characteristics of seepage field and hydraulic gradient based on the above parameters and seepage theory so as to analyze the leakage amount of reservoir water permeating through the overburden layer under different operation conditions. In view of the above study, the simulation results of hydraulic gradient under different conditions are analyzed to assess the seepage stability of the dam foundation, which is further compared with the preliminary estimate so that the final conclusion can be derived.