Study on surface settlement and structural deformation for large span subway station using a new pre-supporting system

A new construction pre-supporting system, Steel Tube Slab system (STS), is proposed for large underground space excavation with shallow depth. The adjacent steel pipes in STS method are connected by a couple of flanges, bolt and concrete in order to improve the flexural capacity and lateral stiffness of the whole structure. STS method is firstly adopted to construct the ultra-shallow buried and large span subway station in China. Ground settlement and structural deformation are monitored during the construction. A numerical model is established for the subway station, the reliability of the numerical model is verified by comparing the numerical results with monitored data. The influence of large span underground excavation on surrounding soil and existing buildings in soft soils are investigated. Results prove that STS method can effectively control and reduce the ground settlement during construction. This study can provide a strong guidance for application of STS method in soft soils.