Abstract: To accurately assess the impact of foundation pit excavation on the structural safety of adjacent rail transit facilities in a rheological soft soil environment, a case study is conducted on the Shanghai Jinqiao Metro Over-track Project. Based on finite element numerical simulation methods and field monitoring data, the deformation of the metro track bed and the settlement of the surrounding ground surface during foundation pit excavation are analyzed. Additionally, the influence of combined control techniques, such as "full-area reinforcement with triaxial deep stirring piles and metro jet system (MJS) piles on the adjacent metro", on the deformation of the metro track bed during foundation pit excavation is examined. Research indicates that: (1) Reinforcement construction using the MJS method induces track bed heaving, with its effect decreasing outward from the edge of the foundation pit. The maximum impact zone is concentrated near the centerline of the foundation pit, and the heaving value gradually decreases over time after construction is completed. (2) The foundation pit excavation causes the west side of the metro track bed to heave in an M shape, with the excavation of the first two layers of soil contributing significantly to the increase in heave. (3) The metro track bed adjacent to the riverbank subsides due to foundation pit dewatering and seepage, with a maximum settlement of 1.44 mm. (4) The surface on the north and south sides of the foundation pit undergoes uplift and subsidence, respectively, manifesting as a "spoon-shaped" distribution and a spatially decaying distribution. (5) Following soil reinforcement using MJS piles and triaxial deep stirring piles, the vertical displacement of the track bed is significantly reduced, by nearly 40%.

Key words: rheological soft soil, deep foundation pit, existing metro station, reinforcement