Hydro-mechanical behavior of a deep excavation with dewatering and recharge in soft deposits

Abstract

Dewatering is mandatory for deep excavations above confined aquifers. Artificial recharge is then commonly used to alleviate the adverse impacts of dewatering. Together, these construction technologies complicate stratum responses including groundwater flow and stratum deformations. This study conducted a coupled hydro-mechanical numerical analysis on a case history of a deep excavation with dewatering and recharge construction measures. The numerical model and input parameters were validated by field data. Results of drawdown distributions, pore pressure variations, vertical effective stress and stratum deformations were analyzed in association with construction activities. It is found that the drawdown of the confined aquifer was closely correlated to dewatering and recharge activities. The excavation-induced settlement mainly occurred in soft soil layers, whereas the stratum deformation induced by dewatering and recharge occurred in the aquifer and adjacent aquitards. The distinct stratum responses could be attributed to different changes in pore pressure and effective stress induced by excavation, dewatering and recharge.