Progressive failure mechanisms of segmentally assembled shield tunnel linings with continuous longitudinal joints under localized damage

The shield tunnel is assembled from numerous segments which are connected by bolts, resulting in the presence of many joints within the structure. These joints significantly weaken stiffness and integrity of the structure, making them weak points. Under certain extreme conditions, local failures can occur in shield tunnels, easily triggering large-scale progressive failure. However, the mechanism of progressive failure in shield tunnels is not yet fully understood. Based on previous studies of the mechanical behaviors of tunnel joints under various loading conditions and the CEL method, a three-dimensional numerical model is established, successfully replicating the progressive failure process in shield tunnels. The study identifies four stages in the progressive failure process: collapse of the initial damaged ring (IDS ring), circumferential joint response, longitudinal joint response, and termination of the progressive failure.