Hydro-mechanical coupled analyses on wall deformations caused by deep excavations and dewatering in a confined aquifer

This study investigates the effect of dewatering on wall deformations of deep excavations through numerical analyses. A hydro-mechanical coupled method is proposed for deep excavations with dewatering activity. The groundwater flow and soil consolidation are described by Darcy’s law and Biot consolidation theory, respectively. The coupled method is validated by a case history in Shanghai, China. A hypothetical excavation model considering the typical distribution of Shanghai strata is developed. Deep excavations with and without dewatering in the confined aquifer are simulated for comparison. The wall deformations for the two scenarios are compared, and the lateral pressure acting on the wall is discussed to interpret the deformation behavior. Besides, the wall insertion depth, discharge rate, and hydraulic conductivity of the confined aquifer are changed to analyze their influences on wall deformations. Results indicate that dewatering during deep excavation reduces the excavation-induced wall deformations. It is mainly attributed to the fact that dewatering can decrease the external load acting on the wall and increase the resistance on the excavated side. The parametric analyses indicate that wall deformations decrease as the insertion depth increases when it is partially penetrated into the aquifer, and increasing discharge rate or decreasing hydraulic conductivity for the confined aquifer could result in smaller wall deformations.