【摘要】 本文通过模型试验揭示了有关沟后面板砂砾石坝溃坝的原因．单纯是面板顶端接缝漏水只出现垂直向下的渗流，上部下游坝坡没有逸出水流．接缝漏水同时面板顶端与坝体之间大范围的相脱开，才会再现上部下游坝坡逸出渗流．溃坝前坝体中部并未全饱和．溃坝机理是坝顶存在ｋ＞１０ｃｍ／ｓ且呈上下游连通的极强透水层，面板顶端又是脱开坝体的，接缝漏水使极强透水层与库水直接相连通，因而产生较大的水平向的水力比降，使之管涌和接触冲刷，同时渗流冲刷坝坡，引起崩塌．最后防浪墙失稳倒塌，库水漫顶而下，最终溃决．更多还原

【Abstract】 The cause of the dam breach are revealed by model test. The following conclusions have been drawn:1. if large amount of water leakage happened at the joint of concrete face and the bottom of wave wall, the seepage in dam can only be a vertical seepage so the seepage water cannot be drained out from downstream slope above EL. 3260; 2. only when the upper part of the concrete face is separated from the dam body and the separated section reaches EL. 3270, the leakage water from the joint can flow out at EL. 3260 of the downstream slope; 3. before the breach, the dam body was not totally saturated; 4. because there is a highly permeable piping layer, it causes piping and contacting erosion and the drained water will scour the downstream slope and cause sloughing. Under the action of piping, scouring and sloughing the wave wall collapsed and at last the breach happened.更多还原