Assessment of ground settlement induced by foundation pit dewatering near an aquifer-penetrating metro station

Pre-existing underground structures would affect groundwater flow (i.e., water-blocking effect) and soil deformation (i.e., soil-blocking effect) during pit dewatering in dense urban environments, leading to ground responses different from those in scenarios without underground structures. In this study, a series of numerical models were developed to investigate water‑soil‑structure interaction, considering the barrier effect of an adjacent metro station embedded in multiple aquifers. The results demonstrate three key findings. First, the cut-off ratio of the station relative to the dewatering aquifer has a great effect on the water-blocking effect; a ratio exceeding 0.5 would significantly intensify the effect, resulting in considerable groundwater drawdown in front of the station and differential drawdown on both sides of the station. Second, the intensity of the two blocking effects is governed by the combination of the pit-station distance (D) and the station burial depth (H). A larger D and a larger H enhance the water-blocking effect, thereby increasing the ground settlement; however, a smaller D and a larger H intensify the soil-blocking effect, thereby reducing the settlement. Third, unified relationships of drawdown versus H and settlement versus H are proposed for preliminary analysis of dewatering-induced ground response under the barrier effect. The findings can help identify the dominant blocking effects and quantify key parameters, thus optimizing dewatering design in similar soft soil areas.