三峡一期围堰运行后的调查与试验

三峡一期围堰安全运行３年后拆除，堰体大量有用当地风化砂，其中↓Δ７０ｍ以下的水下抛填，最大抛填深度２５ｍ，对部分风化砂进行了调查和物理，力学性能试验，证明水下抛填不会产生大的颗粒级配分离现象，千密度可满足设计要求，堰基淤砂层不全产生振动液化，柔性材料防渗墙运用３年后，墙厚及力学性能均满足设计要求。

Investigation and tests after operation of first phase cofferdams

The first phase cofferdams at the Three Gorges Project were removed after they operated for 3 years. The embankment bodies were made of the local weathered sand, of which the portion below EL. 70 m was placed underwater, with a maximum backfill depth of 25m. The investigation and the physical and mechanical tests on the weathered sand have shown that the separation of grain gradation backfilled under water could not occur, The dry density could meet the design requirements, and the liquefaction resulting from vibration could not occur in the sedimentation on which the cofferdams were based- During the 3 -year operation, the thickness and the mechan-ical properties of the cut -off wall made of flexible materials all met the design requi-rements.