A Method for Calculating the Deformation of Existing Bridge Pile Foundations Caused by the Oblique Crossing of Shield Tunnels

This paper presents a theoretical study of pile deformation caused by shield tunnels obliquely crossing adjacent existing bridge pile foundations. The method for calculating the deformation of existing bridge pile foundations caused by the oblique crossing of shield tunnels was established via the modified Loganathan formula, Kerr model, and load transfer method. The reliability of the proposed method was validated according to field monitoring results and relevant case analysis results. Besides, the main factors influencing the pile deformation were analyzed via the proposed method. The results suggest that the proposed method can obtain the horizontal deflection deformation and vertical displacement of the pile caused by a shield tunnel obliquely crossing an existing bridge pile foundation. It is also applicable to calculate the pile deformation caused by orthogonal crossing and oblique crossing of the shield tunnel. The theoretical calculation results of pile displacements are all well-fitted to the field monitoring results. Compared with other methods, the theoretical calculation results obtained by the proposed method are similar to the field monitoring results, which shows higher calculation accuracy. Except for the pile cross-section radius and the shield tunnel excavation radius, the horizontal distance between the center axis of the pile foundation and the center of the shield tunnel and the oblique crossing angle between a shield tunnel and an existing pile foundation are both negatively correlated with the vertical pile displacement. The shield tunnel excavation radius is positively correlated with the horizontal deflection pile deformation, and the rest of the aforementioned factors are all negatively correlated with the horizontal deflection deformation of the pile. Therefore, the aforementioned parameters should be predicted in advance and controlled within a reasonable range to mitigate the adverse effects of the existing bridge pile foundation caused by the oblique crossing of the shield tunnel.