Transverse deformations and internal forces of tunnel segments caused by construction of steel casings of bridge piles

In order to reasonably evaluate the health status and long-term service performance of tunnel structures under the construction influences of bridge piles, it is necessary to conduct an in-depth study on the transverse force and deformation characteristics of the tunnel segments. Based on the results of the additional stress under construction of a bridge pile, firstly a formula for calculating the additional confining pressure considering the stiffness of the existing tunnel is proposed, and the additional confining pressure distribution of the tunnel is obtained during the construction of the steel casing of the bridge pile. Then, based on the shell-spring model, a three-dimensional numerical simulation of the segment is established, and the laws of the transverse deformation and internal force of the tunnel segments are discussed. Finally, a method for identifying the rotation behavior of the tunnel is defined, and the performance index of the local deflection of the segment is proposed. The results show the calculated results are more consistent with the measured data. As the construction depth of the steel casing of the bridge pile increases, the tunnel moves to the left firstly and then tilts to the right, which eventually leads to the overall settlement and the "vertical ellipse" deformation of the tunnel as a whole. After the bridge pile is constructed to the depth of the tunnel axis, the tunnel convergence changes drastically and enters the difficult-to-control phase of the development of the lateral deformation of the tunnel. The zero value of bending moment and the maximum value of shear force are mostly located at the joints of the adjacent segments, so the joints with larger shear force are more prone to diseases such as misalignment, water leakage, etc. During the construction of the steel casing of the bridge pile, the tunnel segments have undergone a transition from clockwise rotation to counterclockwise one, and the critical point is in the range of 0.85D below the buried depth of the tunnel axis.