Analysis And Research On Dewatering And Surface Settlement Law Of Subway Deep Foundation Pit In Soft Soil Area

In recent decades,the foundation pit engineering has begun to develop in a deep,long and large direction,and the environmental conditions have become increasingly harsh.With the increase of foundation pit depth,the influence of groundwater on the safety and stability of foundation pit engineering becomes more and more important.Dewatering of foundation pit has become an indispensable auxiliary measure for foundation pit excavation.Located in the eastern part of North China Plain,Tianjin has been affected by many transgressions and regressions in history.There are deep soft soil layers,mainly composed of clay,silty clay,silt and silt.The hydrogeological conditions are complex,the amount of diving water is large,the water level is high,and there are multi-layer confined water and high water head.Complex hydrogeological conditions bring great difficulties to dewatering of foundation pit.Based on the deep foundation pit engineering of a station in the first phase of Tianjin Metro Line 10,according to the relationship between the retaining structure of the foundation pit and hydrogeology,this paper adopts the precipitation schemes of diving in the pit,combing and dewatering outside the pit.Combined with the field pumping test before the foundation pit excavation construction,to determine whether the dewatering scheme meets the needs of the foundation pit excavation,and combined with the monitoring data of the test,to optimize the dewatering scheme of the foundation pit.Finally,the land subsidence caused by foundation pit dewatering is estimated by finite difference method,and compared with settlement monitoring data during foundation pit excavation,which provides a reference for similar projects.