Abstract: When only a portion of the shield lining structures in a full-line tunnel are overloaded, their bearing and failure characteristics are significantly different from those in the full-line overloaded case. In existing studies, one or several segmental lining rings have been studied, with overload applied to selected lining rings to analyze the performance evolution of the lining structures; however, this approach fails to reveal the bearing and failure characteristics of shield lining rings under localized overload. To address this research gap, we employ 3D finite element modeling to investigate the mechanical performance and failure mechanisms of shield segmental linings under localized overload conditions, and compare the results with full-line overload scenarios. Additionally, the impact of reinforcing shield segmental linings with steel rings is studied to address issues arising from localized overloads. The results indicate that localized overloads lead to significant ring joint dislocation and higher stress on longitudinal bolts, potentially causing longitudinal bolt failure. Furthermore, the overall deformation of lining rings, segmental joint opening, and stress in circumferential bolts and steel bars is lower compared to full-line overloads. For the same overload level, the convergence deformation of the lining under full-line overload is 1.5 to 2.0 times higher than that under localized overload. For localized overload situations, a reinforcement scheme with steel rings spanning across two adjacent lining rings is more effective than installing steel rings within individual lining rings. This spanning ring reinforcement strategy not only enhances the structural rigidity of each ring, but also limits joint dislocation and reduces stress on longitudinal bolts, with the reduction in maximum ring joint dislocation ranging from 70% to 82% and the reduction in maximum longitudinal bolt stress ranging from 19% to 57% compared to reinforcement within rings.

Key words: Shield segmental lining; Localized overload; Failure characteristics; Steel ring reinforcement

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