深厚覆盖层广泛分布于我国大江大河中，开展其研究对加快我国水利水电工程建设具有重大意义。在深厚覆盖层地基上建坝首要解决的是大坝的基础防渗问题。对工程算例进行了二维渗流场数值分析，结果表明：在深厚覆盖层地基上延长水平黏土铺盖至4倍上游水头可以减少渗漏量；大于4倍上游水头时，继续增加铺盖长度对渗流量无影响；只有当混凝土防渗墙深度大于3/4倍地基覆盖层厚度时才能取得较好的防渗效果；当防渗墙完全封闭覆盖层时能够可靠、有效地截断水流。

 Deep overburden distributes widely in rivers of our country, in which case the study is of great significance to speed up our country water conservancy and hydropower project. To build a dam on the deep overburden foundation, the first problem to solve is the seepage of the dam foundation. In this paper, two-dimensional numerical seepage analysis methods is used for project instances. The analysed result shows that it can decrease the amount of seepage when the length of clay waterproof blanket on the deep overburden foundation is 4 times upstream water head, that it doesn’t effect the amount of seepage when its length is more than 4 times upstream water head；that it can receive better effect of anti-seepage when the depth of cut-off wall is over 3/4 times thickness of deep overburden, and that it can cut off water flow reliably and effectively when the deep overburden are completely closed by the cut-off wall.