Mechanism of two-side effect of dewatering in deep excavation: Mitigating wall deflection but aggravating ground settlement

Groundwater seepage and stratum deformation induced by excavation dewatering are substantially influenced by adjacent underground structures. The response of an excavation varies considerably depending on the presence or absence of such structures. Based on an actual engineering project, a laboratory‑scale model test system for excavation dewatering was developed. By monitoring the variations in groundwater level outside the excavation, ground surface settlement, enclosure wall deflection, and lateral pressures on both sides of the wall, this study investigates the mechanism by which adjacent deep‑buried underground structures affect dewatering‑induced ground deformation. The results indicate that (1) the pre-existing structure alters the groundwater seepage path and impedes recharge to the excavation. Consequently, the groundwater inflow into the excavation is lower compared to scenarios without such a barrier; (2) as the burial depth of the adjacent structure increases, the water‑blocking effect becomes more pronounced, leading to a reduced flow rate and smaller enclosure wall deflections. At the same time, this results in a larger water level difference across the enclosure wall and increased ground settlement outside the excavation. In practice, engineers should consider the barrier effect induced by adjacent deep‑buried underground structures during foundation pit design to achieve an optimal scheme.