Abstract: In order to study the optimal combination depth of suspended impervious curtain and dewatering well filter in deep foundation pit dewatering project, and optimize the dewatering scheme of deep foundation pit, the deep foundation pit debasement project of Qingnian Road Station of Nantong metro was chosen as a case study, and the groundwater seepage theory and Terzaghi one-dimensional consolidation theory, a coupling mathematical model of three-dimensional groundwater seepage and land subsidence considering the variation of soil parameters with the consolidation process was established and solved by the finite element method. Using pumping test data, the visual numerical model was identified and verified. By controlling the water level in the pit and the ground settlement outside the pit, the number of pumping wells and the pumping rate were optimized, and the optimal position of the filter under three working conditions of plugging the impervious curtain into the aquifer was simulated and predicted. And the three schemes from the construction period, cost and safety and reliability and other aspects of comparative analysis, it is concluded that when the impervious curtain is inserted into the aquifer at a depth of 1/2, the filter of the dewatering well is inserted at about 9/50-9/20, that is , the buried depth at the bottom of the impervious curtain is 46.2 m,and the buried depth of the filter is 33.7-42.7 m, 17 pumping wells are adopted for dewatering as the optimal scheme.

Key words: deep foundation pit dewatering, land subsidence, suspended impervious curtain, finite element method