Research on the deformation response of shallow-buried metro station constructed using small pipe-roof - top slab method: A case study

The construction of metro stations using conventional underground excavation methods often faces challenges such as difficulties in controlling ground settlement, prolonged construction periods, and complex procedures. Therefore, this study proposes a new construction method for the coordinated support of small-diameter pipe-roof and permanent station top slab: Small Pipe-roof – Top Slab Method (SP-TS). Using the Heping South Street Station of Shenyang Metro Line 3 as a case study, systematically elaborates on the complete construction process of the SP-TS method. Based on field monitoring data, reveals the development patterns of ground settlement, building settlement, and pilot tunnel deformation (including arch settlement and convergence) during construction. Subsequently, a three-dimensional refined numerical model was established to analyze the influence of key design parameters on ground settlement. Finally, through comparison with stations constructed using other methods, the technical superiority and applicability of the SP-TS method under specific conditions are demonstrated. The research results indicate that during the construction of the SP-TS station, the excavation of soil between the pilot tunnels and the construction of the top slab, accounted for approximately 85 % of the total settlement. The final settlement of surrounding buildings remained below 2 mm, while the arch settlement and horizontal convergence were about 4 mm and 2 mm, respectively. The stiffness of the pipe-roof demonstrated the most significant influence on settlement control; when the flexural rigidity (EI) was increased to 2EI, settlement decreased by 8.2 mm. In comparison with other underground excavation methods such as PBA, the SP-TS method reduced settlement by up to 60 % and shortened the construction period by 50 %. The SP-TS method proposed in this study offers a valuable reference for the construction of underground stations in complex environments.