## 5 Conclusions
A comprehensive analysis is conducted to assess the impact of axial forces, bolts, and tongue-and-groove connections on the torsional-shear performance of segment joints. The findings offer valuable insights for the structural design of TBM tunnels. It is observed that the torsional shear performance of segment joints exhibits significant variation under different axial forces, highlighting the need to consider the pushing force during TBM tunneling when designing segment joints. In cases of substantial torsional deformation, the bolts and tongue-and-groove structures are identified as the primary locations of failure within segment joints. Consequently, the design of these components should incorporate considerations for the torsional deformation of the lining rings to enhance the structural integrity and reliability of the tunnel segments. 5. This study investigates the effects of torque on shield tunnels at the segment joint level, providing insights into the mechanical behavior and performance of segment joints under torsional loads. Recognizing that a shield tunnel operates as a structural system comprising segments and connecting bolts, future research could extend the scope to explore the influence of torque at the lining ring level. In terms of constitutive modeling, the Concrete Damage Plasticity (CDP) model employed in this study has demonstrated its effectiveness in simulating the mechanical behavior of concrete. For the bolts, a bilinear ideal elastic-plastic constitutive model was applied; however, this approach does not account for bolt fracture behavior under ultimate load conditions. Future investigations could enhance the constitutive model for bolts to better capture the failure mechanisms of segment joints under extreme torque. Additionally, this study compares the torsional-shear performance of segment joints with and without mortise and tenon structures, based on structural designs from actual projects. To further refine these findings, future research could examine the influence of mortise and tenon dimensions and geometric parameters on the torsional-shear performance of segment joints, thereby proposing optimized design strategies for improving the overall structural resilience of shield tunnels. Conceptualization, J.C., W.C. and C.D. ; methodology, J.C., M.X. and D.S. ; data curation, W.C. and C.D. ; data analysis, R.D. and D.S. ; writing--original draft preparation, W.C.; writing--review and editing, D.S. ; supervision, J.C.; project administration, C.D. ; funding acquisition, R.D. and M.X. All authors have read and agreed to the published version of the manuscript. This research was funded by Science and Technology Research Project of China Railway Fourth Survey and Design Institute Group Co., Ltd. (2022K088-W01); Shenzhen Science and Technology Project (20220808143139001); The Shenzhen University 2035 Initiative (2022B007). Not applicable. All data included in this study are available upon request by contact with the corresponding author. Author [PERSON], [PERSON] and [PERSON] was employed by the company China Railway Siyuan Survey and Design Group Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.