Qian Fang

This study presents a comprehensive investigation into the deformation mechanisms of existing metro stations subjected to the simultaneous construction of adjacent foundation pits and underground tunnels. A refined three-dimensional numerical modeling framework is developed to simulate the entire construction process, capturing the complex interactions between excavation activities and station structures. The modeling encompasses deep excavation, side-crossing, and overcrossing passage construction, and the staged installation of support systems. Six construction schemes, varying in excavation sequence, interlayer thickness (clear distance), and passageway layout, are systematically analyzed. Field monitoring data are incorporated to validate the numerical models, enhancing the reliability of the results. The analysis identifies the construction sequence as the primary factor influencing station deformation. Specifically, the strategy of constructing passageways first, followed by excavation of the interchange hall, effectively reduces both vertical and horizontal displacements by leveraging the early-stage portal-frame reinforcement effect. Increasing the clear distance between new structures and the existing station helps mitigate construction-induced deformation, although the benefits plateau beyond a certain threshold. Sensitivity analysis shows that overcrossing passages are most sensitive to variations in clear distance, followed by foundation pits and side-crossing tunnels. Additionally, the spatial positioning of passageways significantly impacts deformation magnitude and propagation. Passageways near expansion joints cause the greatest uplift, while those placed at mid-span experience minimal disturbance due to enhanced structural stiffness. This research provides a quantitative understanding of metro station deformation under concurrent construction activities and offers practical insights for optimizing excavation sequences, structural layouts, and interlayer spacing. The findings contribute to ensuring structural safety and minimizing risks in densely built urban metro environments.