Cause Analysis of Seepage Disaster in Deep Foundation Pit of Metro Station in Karst Stratum

Objective In-depth study should be made on the seepage stability during deep foundation pit excavation in water-rich karst stratum in consideration of the water inrush disaster at the side wall or bottom of the pit during excavation construction in water-rich karst areas. Method Based on the deep foundation pit excavation project of Zhongshan Park Station on Foshan Metro Line 3, an in-depth research is conducted on the seepage characteristics of the deep foundation pit and the mechanism of water inrush at the pit bottom. A three dimensional numerical model of foundation pit, soil and karst cave is established, and the equivalent permeability coefficient method is used to make a coupling simulation of the seepage field in karst stratum. Result & Conclusion Through simulation and analysis, the law of water content in karst area of heterogeneous stratum influencing the seepage field and water inrush quantity of the foundation pit is obtained. The evolution characteristics of vertical average hydraulic gradient of the soil at the foundation pit bottom is clarified, and the mechanism of water inrush at the foundation pit bottom in karst area is revealed. The research results can provide reference for the design and construction of deep foundation pit project in water-rich karst area.