Monitoring and Analysis of Mechanical Response of Main Tunnel Structure During Segment-Cutting Process

This study analyzes the deformation and internal force changes of the main tunnel during the cutting process of the pipe jacking method for cross passages. A combination of field monitoring and numerical simulation was used to investigate a construction case of the pipe jacking method for the cross passage of Zhengzhou Metro Line 12. The study provides an in-depth analysis of the stress characteristics of the main tunnel structure during the segment-cutting process. The research findings indicate that during the pre-support stage, the internal support system helps to disperse external water and soil pressure, thereby reducing the internal forces and deformation of the tunnel. In the segment-cutting stage, the horizontal diameter of the main tunnel near the hole location gradually increases, while the vertical diameter decreases. At the same time, the stress on the bolts also rises, with the circumferential bolt stress exceeding that of the longitudinal bolts, eventually approaching their yield strength. The upper and lower ends of the tunnel opening are cut to form cantilever ends, leading to inward converging deformation. This deformation causes the internal forces to disperse toward both sides of the opening, resulting in a noticeable increase in internal force at the 90° position of the semi-cutting ring. The research findings provide a theoretical reference for understanding the deformation patterns and internal force transfer mechanisms of the main tunnel structure during the construction process of cross passages using the pipe jacking method.