Mechanical Response Analysis of the Pile Foundation of the Shield Undercutting Replacement Bridge

As a typical representative of the application of urban underground space, subway lines inevitably conflict with the foundations of existing buildings (structures). In this paper, in order to solve the problem of cross conflict between the shield tunnel and the pile foundation of existing bridges, with the background of an actual buttressing project, the finite element method was used to establish a model of the buttressing pile foundation of a bridge under a shield tunnel. Then, numerical simulation analysis was carried out on the basis of the model of the buttressing pile foundation of existing bridges under the shield tunnel, which includes surface settlement, vertical displacement of the bridge surface, displacement of the original pile and static pile caused by shield tunnel construction of the right line of the tunnel. The changes of pile axial force and the stress response of the buttress beam are analyzed and discussed, and the following conclusions are obtained: Firstly, the peripile frictional resistance of the pile foundation has a certain inhibiting effect on the reduction of soil settlement due to the influence of tunnel construction. Secondly, the beams and cover beams can play a certain role in the deformation coordination during the construction process. Again, in the process of shield tunneling, under the influence of tunneling pressure and grouting pressure, the original piles and hydrostatic piles will produce certain bending deformation in space. Finally, in the process of shield driving, the soil above the tunnel will settle downward, which will lead to the generation of negative frictional resistance under the influence of the coordinated deformation of the bearing platform and the remaining pile.