Ultimate load-carrying capacity of the longitudinal joints in segmental tunnel linings

摘要

According to the service conditions of operating metro shield tunnels, segment joints are vulnerable locations in tunnel linings. In addition, the mechanical performance of segment joints directly determines the bearing capacity of segmental tunnel linings. Illustrated with the typical segment joints of the Shanghai Metro rapid transit system, experiments are conducted to investigate the ultimate bearing capacity of the longitudinal joints under different load conditions. The failure mechanisms of segment joints are introduced. The corresponding analytic model is developed to calculate the bearing capacity of the longitudinal joints during the whole loading process. After verification, the proposed model is further employed to compare the mechanical behavior with full section models. It is found that the failure mode of positive bending moment joints is similar to that of a large eccentricity stress cross section, while the failure mode of positive bending moment joints is similar to that of a small eccentricity stress cross section. What's more, the caulking structure is found to be able to offer the safety margin of structures, which could contribute to the protection of operated subway tunnels.