Action Path and Mechanism of Segment Joints in the Failure History of Shield Tunnel Lining

Focusing on the failure history of single-ring segmental lining structure, the action path and mechanism of segment joint on the segment bending moment was investigated in this study. The explicit equations of segment bending moment increment difference and segment bending moment diffusion coefficient were derived, and the causes of segment bending moment state variation in high load level were studied. In the failure history of segmental tunnel lining, the bending moment variation was mainly controlled by the bending moment increment difference per unit time (IND). IND was mainly controlled by the relative stiffness ratio of segment joints and their derivative. The action path of segment joints on segment internal force can be divided into: 1) the opening and yielding of segment joints, 2) the attenuation of rotational stiffness of segment joints, 3) the change of relative stiffness ratio and its derivative, 4) the IND value of non-zero, and 5) the drastic change of segment bending moment state. Furthermore, the rotation stiffness of the segment joint attenuated, and then the acceleration variation of segment bending moment was caused by segment joint effects because IND was not equal to 0, i.e., the segment bending moment increased or decreased sharply.