土工合成材料在三峡一期土石围堰中的应用

Application of geotextile to first stage cofferdam of Three Gorges Project

三峡水利枢纽一期土石围堰堰体主要由风化砂、石渣和块石填筑而成。三峡坝区粘土料源短缺，若在一期土石围堰上采用粘土心墙防渗，势必影响茅坪溪防护大坝和三期上游土石围堰防渗体储备土料的数量；若全部采用柔性材料防渗墙，将增加围堰工程造价，且围堰很难在一个枯水期完建，影响三峡水利枢纽一期导流的顺利进行。土工合成材料具有施工方便、迅速，成本低，适用性强等优点，且其水上施工技术更趋于成熟。一期土石围堰防渗主要采用两布一膜的土工合成材料、下接柔性墙的防渗型式，加快了围堰施工进度，创造了一期基坑提前抽水条件，为三峡水利枢纽正式开工奠定了坚实的基础。

The first stage earth rock fill cofferdam of Three Gorges Project is mainly composed of the weathered sand, excavated spoil and rock blocks. In Three Gorges dam area, the clay is of shortage. If a clay core wall is adopted for seepage prevention in the first stage earth rockfill cofferdam, it will result in more difficulty in the construction of Maoping dam and the third stage upstream earth rockfill cofferdam. And, if the flexible seepage proof wall is adopted in whole earth rockfill cofferdam, the cost of cofferdam will rise, and the cofferdam could not be completed in a low-flow period, thus, affecting the conducting of the first stage river diversion on time. Therefore, the geotextile was selected for seepage prevention of the cofferdam body above the top of the seepage proof wall. And, the progress of cofferdam construction was speeded, resulting in the dewatering in the foundation pit ahead of schedule.