新疆下坂地水利枢纽坝基深厚覆盖层防渗墙施工

Construction of cutoff wall of deep overburden layer of Xiabandi Hydro-complex in Xinjiang

下坂地水利枢纽坝基覆盖层厚度达150 m,主要以漂石、块石、砾石及砂为主。坝基防渗采取上部素混凝土防渗墙,下接帷幕灌浆方案。防渗墙最大槽孔深90 m,最大墙深85 m。成墙施工设备为冲击反循环钻机、抓斗和冲击钻机。施工中采用地面钻孔爆破、水下定向聚能爆破、重锺冲凿等特殊生产工艺,成功处理了履盖层中夹块石、漂石问题。同时还克服了漂石层钻孔成槽、大漏失量地层处理、塌槽等施工困难,保证了防渗墙施工有序进展和施工质量。

The thickness of deep overburden layer of Xiabandi Hydro - complex reaches 150m, which mainly consist of boul- der, rubble, gravel and sand. The plain concrete cutoff wall is designed for upper part of dam foundation and curtain grouting for the lower part. The deepest hole reaches 90 m and the deepest wall reaches 85m. The wall formation equipment includes percus- sive reverse circulation driller, grab bucket and percussion driller. The rubble and boulder were successfully treated by ground drilling blasting, submerged directional cumulative blasting and impact by heavy hammer. In the meantime, the difficulties of groove formation by hole drilling in boulder stratum, and serious seepage layer treatment and groove collapse were overcome and the construction of cutoff wall was promoted orderly.