Mechanical response of transition segments during the docking construction of the shield tunnel: A case study of Jiangyin-Jingjiang Yangtze River Tunnel

This paper presents a case study of the mechanical response of the transition segments during the docking construction of the Jiangyin-Jingjiang Yangtze River Tunnel in China. The construction method of docking in the highly permeable sand layer was adopted, which is the first case in the world. During the docking construction, complex loading conditions such as grouting, freezing, filling, dismantling, and pouring can easily lead to significant deformation of the segments in the transition section. However, the mechanical response of the transition segments during the docking construction is still unclear. In this paper, field tests and numerical simulations were utilized to examine the evolution and distribution of convergence deformation during the docking construction of the Jiangyin-Jingjiang Yangtze River Tunnel, and to investigate the mechanical responses of transition segments and reinforced steel plates in this process. The results showed that the circumferential and longitudinal stress fluctuations of the segments near the butt docking section were large during the docking construction, while those of the segments far from the butt docking section were small. The relative displacement trends of the vault of each segment along the tunnel axis were consistent, with values ranging from 8.3 mm to 13.0 mm, indicating overall stability of the tunnel. A good agreement was achieved between the numerical simulation results and the field test data, which demonstrates that the numerical model can effectively reproduce the mechanical responses during the docking construction of the Jiangyin-Jingjiang Yangtze River Tunnel. The horizontal convergence deformation of the segments was significantly greater than the vertical convergence deformation, with the former being 2.5–5.0 times greater than the latter. The convergence deformation of the segments before reinforcement was 1.5–2.0 times greater than that after reinforcement, with a maximum reduction of 40.5 % in single-point deformation. The maximum principal tensile stress of the reinforced segment decreased by approximately 63.4 %, and the reinforced steel plate effectively mobilized its tensile capacity within the disturbed core region. This case study can serve as a practical reference for similar tunnel construction projects.