The Influence of Shield Tunneling Characteristics on the Safety of Buildings Above-Case Study for Shanghai Zone

Abstract

The disturbance effect of the shield tunneling process in the soft soil layer on the buildings above the subway tunnel is evident. Studying the spatial position effect of shield tunneling on the buildings above it is crucial for the safety of buildings and for the formulation of reasonable protection measures. Based on the typical soft soil layer in Shanghai, China, this study used Plaxis 3D for the precise simulation of the process of a shield tunnel passing through different spatial positions underneath the buildings above it. Considering the influence of the tunnel position (L), the buried depth (H), and the horizontal distance (D), the law of variation of surface settlement and the internal force and deformation law of overlying buildings during shield tunneling were discussed. The change of the building’s axial force was mainly reflected in the building slab structure, and the change of the shear force and the bending moment was mainly reflected in the building column structure. The box foundation of the buildings played an important role in resisting the influence of shield tunneling. Based on the composite criterion and the strength reduction method, the influence range of the shield tunneling on buildings in the soft soil layer was studied. The variation law of the safety factor of surrounding concrete lining, with or without the building load, was obtained. The influence of the building load on the tunnel construction was reflected by the relative ratio ξ of the safety factor in this case. The inflection point of the ξ curve and ξ = 95% was taken as the boundary of the affected areas that were divided into strong affected areas, weak affected areas, and areas which were not affected.