粉砂粉土地层基坑预降水对环境影响及处理

Effect of pre-dewatering of foundation pit in powder sand soil layer on the surrounding environment and treatment measures

针对南京地铁5号线虹桥站主体基坑预降水阶段引起地下连续墙较大侧移、地表和周边建筑物明显沉降的情况,需采取必要措施确保对周边环境进行保护。本文根据虹桥站基坑预降水试验分析了内外水土压力差、地下水绕流以及预降水工况对周边环境的影响,并对敏感建筑物范围采取坑内抽条加固和钢支撑伺服系统、建筑物与车站基坑之间设置隔离桩、沿建筑物边布设坑外观测兼回灌井、开挖过程中按需降水、必要时对沉降区域采取注浆等处理措施。结果表明:以上措施有效减小了车站基坑开挖期间对周边环境的影响,可确保工程顺利实施。

Aiming at the foundation pit pre-dewatering test of Hongqiao station of Nanjing Metro Line 5,which causes the underground continuous wall to move sideways and the surface and surrounding buildings to settle obviously during,it is very important to take necessary measures to protect the surrounding environment.In this paper,the influences of internal and external water and soil pressure difference,groundwater flow around and pre-dewatering conditions on the surrounding environment are analyzed.In addition,for areas of sensitive buildings,some measures are taken,such as reinforcement with strip pumping in the pit and steel support servo system,isolation piles between buildings and station foundation pit,observation and recharge wells outside the pit laid along the sides of buildings,precipitation as needed during excavation,grouting in settlement area when necessary,etc.The results show that above measures effectively reduces the influence of station foundation pit excavation on the surrounding environment,which can ensure the smooth implementation of the project.