Study on Deformation Law and Reinforcement Effects of Metro Shield Tunnel Segments under Loading and Unloading

［Objective］ Ground loading over metro shield tunnels often causes structural segment deformations, water leakage, and other issues, directly affecting metro operation safety. Based on a case of ground load-induced damage treatment in a Wuhan Metro tunnel interval, the deformation law of metro shield tunnel segments under varying loading conditions and reinforcement measures are investigated. ［Method］ Using the Wuhan Metro damage treatment project as a basis, a three-dimensional numerical model is developed to reflect actual engineering conditions. The model accounts for factors such as staggered assembly and bolt connections of shield tunnel segments. The stress and deformation characteristics of tunnel segments from ground loading and unloading octions under different conditions are analyzed and compared with case study observations. The stress features and deformation behaviors of segments in different scenarios are examined and analyzed. ［Result & Conclusion］ It is found that the tunnel structure remains generally safe when the ground soil column loading does not exceed 1.3 m. When the loading does not exceed 4.0 m, adopting aramid fabric reinforcement at the tunnel crown is the most economical and reasonable solution. For loading exceeding 6.0 m, full-steel ring reinforcement inside the tunnel is more effective. Earlier implementation of reinforcement measures yields better outcomes. During unloading after loading, it is observed that when the ground soil column loading does not exceed 2.0 m, the unloading can result in rebound deformations of more than 50% in the segments. Early detection and timely removal of excessive ground loading are critical to metro maintenance comparison with engineering measurements validate the accuracy of the segment deformation law, the feasibility and effectiveness of the reinforcement measures.