Hydromechanical Response of Deep Metro Station Excavations in Multistrata Soil to Rainfall Infiltration

The increasing frequency of heavy rainfall due to climate change raises concerns about the resilience of underground infrastructure during deep excavations. This study investigates the effects of rainfall infiltration on metro station excavations using a coupled hydromechanical finite-element model, with the Xipu Road Station in Hangzhou, China, as a case study. Simulation results show that rainfall infiltration causes a rapid rise in groundwater level. At low rainfall intensities, the rise is uneven because shearing near the wall reduces the soil void ratio and permeability. At higher intensities, the groundwater level rises more quickly and uniformly due to vertical infiltration combined with lateral seepage from zones with higher void ratios toward the wall. Rainfall also affects wall deformation. In unsupported excavations, wall deflection after rainfall is more than twice that measured before rainfall. In strutted systems, deflection remains nearly constant between struts but increases below the lowest strut, reaching a maximum near the excavation base. Strut forces increase after rainfall, particularly where strut spacing is large, with load increases ranging from 29% to 90% across excavation stages. Rainfall causes greater wall deflection than widening the excavation by 4 m. In contrast, increasing diaphragm-wall thickness from 0.8 to 1.2 m reduces deflection by about 30%, demonstrating the effectiveness of wall stiffness in limiting rainfall effects. These findings provide important insights for improving the safety and resilience of deep excavations under increasing rainfall conditions associated with climate change.