黄壁庄水库除险加固工程副坝混凝土防渗墙施工过程中，发生过7次规模巨大的塌坑事件，为此，对塌坑机理进行了定性分析，总结得出基岩 中存在溶蚀性等裂隙通道、泥浆漏失及存在易失稳砂层是发生塌坑的3个基本要素，砂层漏失形成塌落空洞（渐进发展过程）、塌落空洞致使地面塌陷（短时间完成）是塌坑形成的2个基本环节。采用力学解析方法，对砂层漏失形成塌落空洞的机理进行了分析，并对砂层塌 落的渐进发展过程进行了讨论。采用大变形数值分析方法，通过在砂层中设置塌落空洞，模拟塌落空洞导致地面塌陷的过程。

During concrete cutoff wall construction of Huangbizh uang reservoir secondary dam reinforcement project, seven large -scale ground collapses occurred. This kind of collapse, rarely happened all over the world, is quite different from normal slot collapses during concrete cutoff wall construction, typically caused by mass loss of partia l strata material. By investigating the features of ground collapses, the paper summarizes three elementary factors and two elementary procedures of ground collapses formation. By employing mechanical analytical methods, the mechanism is analyzed that a caving hole would be formed due to the drain of sands in sand-bed. The process of sand-bed progressively caving is discussed also. By means of large deformation numerical method, the pr ocess of ground collapse caused by caving hole in sand-bed, which is set before computation, can be simulated.