Numerical analysis of mechanical response in bridge and pile foundations due to shield cutting of residual piles.

During shield tunneling, interactions with existing structures, such as pile foundations and bridges, are frequently encountered, leading to a growing implementation of shield cutting techniques. This study utilizes a metro tunnel project crossing under a ring expressway bridge in a city in Northeast China to develop a refined three-dimensional finite difference method (FDM) model. The 3D FDM model investigates the mechanical responses of existing pile foundations and the bridge structure due to shield cutting through residual pile foundations. The proposed numerical model is validated against field monitoring data. The simulation results show that the primary mechanical response of the existing pile foundations to shield tunneling is horizontal deformation, which decreases with increasing distance from the tunnel axis. In zones containing residual piles, tunnel crown settlement exhibits a wavy pattern, with lower settlement values compared to areas without residual piles. In contrast, bridge structure deformation remains minimal, with final deformation values below standard values. To comprehensively evaluate the effects of shield cutting through residual piles, the study quantitatively examines stratum disturbances using the ground loss ratio as an indicator. Results reveal that ground loss ratios surrounding residual pile foundations exceed 0.5%, reflecting a substantial influence. A parametric analysis underscores the critical role of ground loss ratios in influencing both bridge structure deformation and tunnel settlement.