Analysis of pumping test and optimization design of excavation dewatering in complex geological environment

Aiming at the dewatering of deep excavation pit in complex and thick confined aquifers, relied on an engineering case in Shanghai, the measured data of pumping test before excavation were verified by numerical simulation, the hydrogeological parameters of each aquifer were obtained through the inversion and verification of the measured data. The ground settlement caused by dewatering with the preliminary designed diaphragm wall was predicted by the verified model, and the comparison of groundwater drawdown and ground settlement under four different diaphragm wall depths was analyzed. The results indicate that ground settlement caused by pumping is large with the existed design of the diaphragm wall depths. The greater the depth of the diaphragm wall, the smaller the ground settlement caused by dewatering. When the diaphragm wall depth is greater than the pumping well depth, the variation of the ground settlement caused by dewatering is small. Considering the environmental effects and the diaphragm wall cost, the optimal depth determined is 48.8 m for the diaphragm wall.