Abstract: When the longitudinal joints with C-T quick connectors are used in shield water conveyance tunnels, the internal water pressure in the tunnel decreases the axial force at the joints, which in turn affects the flexural performance of the joints. However, the axial force effect on the flexural performance of the joints with C-T quick connectors has not been adequately investigated. Therefore, a full-scale compression-bending experiment of C-T quick connector joints under a smaller axial force was carried out in this study. The experiment results were compared with those of the larger axial force experiment with the same joint, and the flexural characteristics of the joint with CT connectors under different axial forces were summarized. The results show that: (1) Under smaller axial force, the flexural process of CT connectors joints can be divided into concrete bending stage and concrete and connectors bending stage. In the concrete bending stage, the moment firstly increases linearly, and then the flexural stiffness of the joint decreases continuously. The flexural stiffness of the joint increases when the C-T connectors are lapped, after which the connectors yields rapidly and the flexural stiffness decreases until the joint failure. (2) Under smaller axial forces, the factors affecting the flexural capacity of the joints are lap, yield, and fracture of the C-T connectors; the tensile properties of C-T connectors need to be improved to prevent premature yielding; while under larger axial forces, the lap and crush of the outer concrete are the critical nodes in the flexural process of the joints. Cracks were observed around the connectors under different axial forces.

Key words: shield tunnel, quick connector, axial force magnitude, longitudinal joint flexural behavior, full-scale experiment