深基坑新老地连墙接缝止水方案比选及分析

Comparison and analysis of sealing schemes for new and old diaphragm wall joints in deep foundation pit

南京长江第五大桥夹江隧道江南盾构接收井基坑围护结构地下连续墙深度为59.9 m,基坑开挖深度达40.1 m,与既有青奥隧道地下连续墙存在两道接缝,且既有青奥隧道地连墙施工时,此处未预留型钢接头,为防止在基坑开挖过程中接缝处发生漏水、漏砂,进而影响在建工程及既有青奥隧道的安全,需要在两道接缝外侧采取有效的封水处理措施。文中提出了3种封水处理措施并进行了施工效果的分析对比,结果表明,高压旋喷桩及盐水冻结法均无法达到止水效果,全套管全回转咬合桩法有效地对新老地连墙接缝起到阻水作用,对类似工况深基坑工程具有参考作用。

The depth of diaphragm wall of foundation pit retaining structure of Jiangnan shield receiving shaft in the Jiajiang Tunnel of Nanjing Yangtze River Fifth Bridge is 59.9 m,and the excavation depth of foundation pit is 40.1 m.There are two joints with the diaphragm wall of the existing Youth Olympic Tunnel.During the construction of the diaphragm wall of the existing Youth Olympic Tunnel,no steel joint was reserved here.In order to prevent the impact from water leakage and sand leakage at the joints during the foundation pit excavation on the safety of the ongoing construction and the existing Youth Olympic Tunnel,it is necessary to take effective water sealing measures outside the two joints.In this paper,three kinds of water sealing treatment measures were proposed,and the construction efficiency was analyzed and compared.The results show that the high-pressure jet grouting pile and salt water freezing method can not achieve the water stop effect.The full casing full rotation occlusal pile method can effectively block the water at the joints of new and old diaphragm walls,and can be used as a reference for deep foundation pit projects under similar conditions.