三峡工程一期土石围堰防渗墙试验

三峡工程一期围堰全长约2500m，采用坝区的风化砂填筑。堰基为淤积粉细砂层（厚度为10～15m）和强风化花岗岩层，在强风化层中残留有直径为0．5～2．5m的球状花岗岩块体。采用防渗墙防渗。为了弄清在回填的风化砂层和堰基粉细砂层中造孔成槽的可行性、造孔时遇到球状花岗岩块体宜采取什么有效措施、何种造孔机具最适用等问题，特在该围堰的上横段取长约356m的一段进行防渗墙施工的现场试验。本文详细介绍了试验情况及其结果。

Constructional experiment with seepage proof wall in an earth rockfill cofferdam

The first stage cofferdam at Three Gorges Project, with some 2500 m of total length, is to be made up of the weathered sand at damsite. The cofferdam foundation consists of the silting silty sand layer with 10~15 m thickness and strong-weathered granite stratum throughout which the spheroidal granite blocks with diameter of 0. 5~2.5 m remain. The concrete wall is to be used as seepage proof element for cofferdam. In order to make sure whether the trench formation by drilling in the cofferdam body composed of weathered sand and its weathered granite foundation with large spheroidal blocks is feasible; what effecti ve measures can be used in case of encountering the large spheroidal granite block when drilling; and which drilling machine is the best one suitable for this work, the field test for constructing the seepage proof wall was conducted at a 356 m long section of first stage cofferdam.