武汉鹦鹉洲长江大桥南锚碇地下连续墙止水措施

Water Stop Measures for Diaphragm Wall of South Anchorage of Yingwuzhou Changjiang River Bridge in Wuhan

武汉鹦鹉洲长江大桥主桥为(200+2×850+200)m三塔四跨悬索桥,该桥南锚碇采用地下连续墙支护的明挖基础,地下连续墙为圆形结构,外径68m、壁厚1.5m,设计深度不小于27.5m。该区域覆盖层厚度较薄,基岩为白云质灰岩,局部裂隙发育,地下水与长江水力联系密切,为做好地下连续墙基础止水,避免发生漏水险情,综合应用了防渗墙、铣接头、墙底嵌岩、帷幕灌浆等止水措施。经基坑开挖前的抽水试验、开挖过程中的监控监测、开挖后的实体验槽证明,地下连续墙墙体、接头缝、墙脚、基岩面均未发生渗水现象,未发生灾害性突水情况,实现了预期止水效果。

The main bridge of Yingwuzhou Changjiang River Bridge in Wuhan is a three-tow- er and four-span suspension bridge with span arrangement （200＋2× 850＋200） m. The founda- tion for the south anchorage of the bridge is the open excavated foundation supported on dia- phragm wall. The diaphragm wall is a circular structure that has an external diameter of 68 m, wall thickness of 1. 5 m and designed depth not less than 27. 5 m. In the area where the dia- phragm wall is located, the overburden is thin, the base rock is the dolomitic limestone with de- veloped local fractures and the underground water there is closely related to the waterpower of the Changjiang River. To stop the water from coming into the diaphragm wall and to avoid the dan- gerous situation of water leakage, a series of the water stop measures of the cutoff wall, cut joints, wall footing rock embedment and curtain grouting was comprehensively taken. The water pumping test before excavating of the foundation pit, the monitoring and control in the process of the excavating and the inspecting of actual trenches after the excavating proved that no water leaked in the wall body, joints, wall footing of the diaphragm wall and in the rock surface, the disastrous water gushing did not occur and the anticipated water stop effect was achieved.