Study on Groundwater System Effect of Tunnel Drainage Control in Karst Valley

A traffic tunnel which is under construction passes through an anticline karst valley area in Chongqing China, in difficult geological conditions. Many buildings lie above the tunnel, the buried depth of which is among 130-150 m; 13 m away from the tunnel on the south side there is a lake about 0.033 km(2) in area and water capacity of approximately 2 x 105 m(3), which mainly accepts replenishment of rainfall and karst water. The geological environment of the site is very fragile and easily affected by the construction of tunnel. Tunnel construction will inevitably cause inrush water and have an effect on groundwater system in the karst valley, which will cause the dropping of groundwater and lake water level, drying up of wells and springs, even karst collapse within the affected area. The key to solve these problems is controlling water drainage during tunnel construction. In this paper, the establishment of a fullscale range of three-dimensional finite element model is based on the analysis of hydrogeological conditions of the karst valley, combined with the supplementary geological survey during tunnel construction, the test of the amount of inrush water, and the research of monitoring data about lake water level. By controlling the permeability coefficient of the rocks surrounding the tunnel, the effect of tunnel drainage control to the karst valley groundwater system is studied, providing reference basis for the tunnel site geological environment protection and tunnel supporting design.CPCI-S(ISTP)jxgcqu@163.com; 269040798@qq.com; liuhongweicq@126.com; jinyuanbms@pku.edu.cn571-57