长江漫滩悬挂式止水帷幕基坑变形规律研究

Study on deformation characteristics of deep excavation with suspended curtain in Yangtze River floodplain

针对因长江漫滩悬挂式止水帷幕基坑降水环境影响特征认识不清而引发的环境问题,以南京长江漫滩地区某悬挂式帷幕地铁基坑工程为背景,建立基坑开挖降水耦合作用的流-固耦合数值分析模型,研究基坑降水开挖耦合变形的一般特征以及地连墙插入比对环境影响的控制作用.研究结果表明:长江漫滩基坑降水具有明显的流固耦合效应,地表总沉降由土体固结以及渗流引起的围护结构侧移导致的地表沉降组成,流固耦合作用下地表沉降量和沉降范围大于非流固耦合作用;流固耦合模式下降水施工前期引起地连墙悬臂形侧移增量,后期引起地连墙类似于踢脚形的侧移增量;非流固耦合模式下,满足基坑结构稳定后,地连墙深度继续增加对其峰值侧移和地表沉降影响甚微,而流固耦合模式下地连墙侧移峰值则先减小后增大,且坑外地表峰值沉降在地连墙一定插入深度范围内呈线性发展.

In response to unclear understanding of the environmental impact characteristics arising from groundwater control using suspended curtains in excavations on the Yangtze River floodplain,this study focuses on a subway foundation pit project in the Nanjing Yangtze River floodplain with a sus-pended curtain.A numerical model for fluid-solid coupling is established to investigate the general characteristics of coupled deformation induced by dewatering and excavation.The study emphasizes the control effect of the insertion ratio of diaphragm walls on environmental impact.The results indi-cate that the dewatering of foundation pits in the Yangtze River floodplain exhibits a pronounced fluid-solid coupling effect.Ground settlement induced by precipitation is composed of soil consolidation and lateral displacement of the retaining structure due to seepage.The ground settlement curve is grooved,with greater settlement and range when considering fluid-solid coupling compared to non-fluid-solid coupling.In the fluid-solid coupling mode,the dewatering construction induces a cantilever-shaped lat-eral shift increment of the diaphragm wall in the early period and a the kick-shaped lateral shift incre"ment of the diaphragm wall in the later stage.In the non-fluid-solid coupling mode,after ensuring the stability of the foundation structure,an increase in diaphragm wall depth has a minimal impact on its peak lateral shift and the maximum ground settlement.However,in the fluid-solid coupling mode,the peak lateral shift of the diaphragm wall decreases first and then increase,and the maximum ground settlement develops in a linear way within a certain insertion depth range.