深厚承压水层下临江深大基坑工程支护结构设计与实践

Design and practice of supporting structure of riverside deep and large foundation pit project with deep confined water layer

基于上海世博B06地块深大基坑工程,根据场地临近黄浦江、场地分布有深厚承压水层、周边环境非常敏感等条件,采取了分坑施工、悬挂式止水帷幕和坑外设置回灌井等一系列技术措施。通过现场单井抽水试验,取得了承压水含水层的详细水文力学参数;通过现场群井抽水试验,获得了承压水水位降深与地面沉降的初步关系。采用数值分析方法建立三维渗流模型,研究了不同止水帷幕深度下,坑内降压对坑外环境的不利影响,并结合坑外环境对象的保护要求,确定了合理的悬挂式止水帷幕深度(42m)。实施结果和监测数据表明,采取的技术措施有效地减小了基坑坑内降压引起的坑外水位降深,保证了周边环境的安全。

Based on the deep and large foundation pit project of Shanghai EXPO B06 block,according to the conditions of the site near Huangpu river,the site distribution with deep confined water layer,and very sensitive surrounding environment,a series of technical measures such as pit-dividing construction,suspended impervious curtain and recharge well outside the pit were adopted.Through the field single well pumping test,the detailed hydromechanical parameters of confined water aquifer were obtained.Through the field group well pumping test,the preliminary relationship between the drawdown of confined water level and land subsidence was obtained.The three-dimensional seepage model was established by numerical analysis method,and the adverse effects of water pressure reduction in the pit on the environment outside the pit were studied under different impervious curtain depths.Combined with the protection requirements of the environmental objects outside the pit,the reasonable impervious curtain depth(42 m)was determined.The implementation results and monitoring data show that the technical measures adopted effectively reduce the drawdown of water level outside the pit caused by water pressure reduction in the foundation pit,which ensures the safety of the surrounding environment.