Deformation Law of Metro Station Underground Excavation by Arch Column Method in Upper-Soft and Lower-Hard Strata

［Objective］ The construction of shallow-buried metro station in upper-soft and lower-hard strata is tough, easily leading to engineering issues such as land subsidence and station deformation. As a new construction method, the arch column method features relatively simpler procedures, lower safety risks and higher construction efficiency. It is necessary to study the deformation law of metro station underground excavation by the arch column method in upper-soft and lower-hard strata. ［Method］ The construction process is numerically simulated to calculate land subsidence, tunnel horizontal convergence and vault subsidence during construction, and the data are compared and analyzed with the actual monitoring data onsite. ［Result & Conclusion］ Simulation results show that during arch column method construction, the maximum land subsidence above the station center-line is 13.91 mm; the maximum clearance convergence of the arch is 0.66 mm, and that of the lower straight wall section is 1.85 mm; the vault subsidence of the middle pilot tunnel is 0.66 mm, and that of the side pilot tunnel is 0.07 mm. On-site monitoring results show that the maximum land subsidence is 19.75 mm; the clearance convergence of the middle pilot tunnel is 3.25 mm; the vault subsidence of the middle pilot tunnel is 7.07 mm, and that of the side pilot tunnel is 3.84 mm.