Seismic performance of double-layer tunnel linings
This research develops a performance-based assessment framework for double-shell tunnel lining systems by explicitly linking inter-lining interface behavior to load transfer mechanisms, damage evolution, and structural failure under seismic loading. Unlike conventional approaches that either neglect the structural contribution of the initial lining or assume simplified composite action, the proposed framework recognizes that the interaction between the initial shotcrete lining and the final concrete lining governs the redistribution of forces, stiffness degradation, and deformation capacity of the system.
Through nonlinear finite element modeling, the study investigates the influence of different interface conditions, including no-slip, relative-slip, and full-slip configurations, as well as the time-dependent deterioration of shotcrete on the global structural response.
The framework establishes performance levels that identify critical thresholds for damage progression, plastic hinge formation, and stiffness reduction across different seismic intensities, thereby providing a mechanistic description of the transition from elastic behavior to localized damage, load redistribution, and ultimate failure. To quantify these complex behaviors, we propose a unified damage index that integrates ductility demand, hysteretic energy dissipation, interface-induced deformation, and stiffness degradation into a single performance metric, enabling a comprehensive evaluation of seismic resilience and providing a rational basis for the design and assessment of modern NATM/SEM double-shell tunnel lining systems.
Reported seismic damage levels for tunnels of various lining types as a function of PGA, after Power et al. (1998), with fitted Damage Index (DI) and Maximum Dynamic Strain (MDS) curves