Effect of Dislocation on Flexural Behavior of Longitudinal Segmental Joint for Shield Tunnel

Joint dislocation is a common problem in shield tunnels that severely affects the safety and durability of tunnels. However, research on the mechanical properties of the lining structures caused by dislocations is insufficient, and its mechanism still remains unclear. This study analyzed the effects of dislocations on the flexural behavior of longitudinal segmental joints using full-scale experiments and numerical simulations. First, full-scale compression bending experiments were performed on joint specimens with initial dislocations under positive and negative moments. Three-dimensional refined numerical models considering the concrete damage of joints with dislocations were established and verified. The loading process and failure characteristics of the joint were summarized by integrating the experimental and numerical results. Numerical simulations of longitudinal joints with different dislocations were then performed to analyze the effect of dislocations on the joint mechanical behavior. The results show that the loading process of the segmental joint with dislocation can be divided into five stages, and the four characteristic points between the stages are bolt stress, severe segment damage, segment top contact, and joint failure. The dislocation effect on the positive moment joint is not evident, whereas the flexural resistance of the joints under a negative moment is significantly affected by the dislocation. The ultimate negative moment bearing capacity decreases by 11. 7%∗ the first-stage stiffness decreases by 22. 8%. and both decrease linearly with an increase in dislocation. Compared to the joint without dislocations, the bolts of the dislocation joint extrude concrete from the bolt hole, causing it to collapse significantly. The segment intrados experience severe damage due to force asymmetry under a negative moment, causing leakage to occur prematurely. Therefore, the dislocation effect on the bearing capacity of the joints is important and cannot be neglected during tunnel operation stage. Consideration should also be given to potential concrete damage and secondary disasters caused by dislocation, such as local concrete crushing resulting from dislocations. © 2023 Xi'an Highway University. All rights reserved.