Abstract: Numerical simulation is employed to analyze the groundwater control effect of super-large deep foundation pit dewatering using partially suspended impervious curtains and partially closed impervious curtains. The influence of different rates of closed impervious curtain (R_c) on the dewatering process and its impact on adjacent subway tunnels are investigated. The findings reveal a gradual decrease in the influence of dewatering on the surroundings at a given R_c as the insertion ratio (L/M) of the suspended impervious curtain increases, with a distinct turning point. Therefore, an economical and reasonable insertion ratio can be determined based on the descending depth variations of the pressure water head. L/M exhibits minimal influence on the water pumping capacity (q) per unit area. In contrast, R_c significantly affects q, showing a good linear correlation when R_c ranges from 0% to 80%. A comparison between calculated results and field monitoring data indicates a notable difference in water head between the inside and outside of a foundation pit, favoring the closed impervious curtain side over the suspended impervious curtain side. Consequently, partially closed impervious curtains prove effective in controlling groundwater seepage in sensitive surrounding areas. Furthermore, deformation calculation results of subway tunnels under different values of R_c could help determine the minimum R_c required to meet deformation requirements. Therefore, partially closed impervious curtains can be employed flexibly in the impervious curtain design for large foundation pits depending on the sensitivity of the surroundings.

Key words: partially-closed impervious curtain, ratio of closed impervious curtain, foundation pit dewatering, seepage of groundwater