Research on the Mechanical Response of Adjacent Rings After Local Damage in Shield Tunnels

Previous incident analyses have unequivocally demonstrated that local failures in shield tunnels can initiate progressive collapse, posing severe threats to structural integrity and operational safety. To systematically investigate the mechanical response of adjacent ring structures subsequent to local damage of shield tunnels, a numerical model dedicated to simulating tunnel local failure was established based on the coupled Eulerian–Lagrangian (CEL) method, enabling quantitative characterization of the stress states of adjacent ring structures under local failure scenarios at different tunnel positions. The findings reveal that an unloading zone and soil arching effect are spontaneously formed in the vicinity of the local failure region following tunnel structural damage. Under the synergistic action of the unloading zone and soil arching, torsional deformation is induced in segments proximate to the local failure area, which consequently results in insufficient torsional bearing capacity of the segments and inadequate shear bearing capacity of the circumferential joints. Furthermore, the influence of local failure on adjacent ring structures exhibits a distinct positional dependence: the closer the failure location is to the tunnel crown, the more pronounced the adverse effects on the adjacent ring, while the impact attenuates significantly on the opposite side of the tunnel. In practical engineering design, it is imperative for engineers to implement targeted reinforcement measures for adjacent rings in potential local failure‐prone zones, and three specific and actionable recommendations are proposed in this study to guide engineering practice.