Seismic resilience assessment of mountain tunnels considering ancillary structures

Mountain tunnels consist of main and ancillary structures, both of which affect seismic resilience. Current research on tunnel seismic resilience has not yet systematically addressed ancillary structures. To bridge this gap, this study proposes a seismic resilience assessment framework incorporating both main and ancillary structures. The framework encompasses seven core elements: establishing hierarchical relationships between the tunnel and basic components; acquiring fragility parameters for main and ancillary structures; quantifying relationships between component damage states and residual functionality; determining tunnel residual functionality via hierarchical belief rule base method; accounting for seismic uncertainties via Monte Carlo simulation, with the mean value from multiple simulations representing final residual functionality; calculating the seismic resilience index by combining residual functionality with the functionality recovery function. Fragility parameters for components of main structures are derived from literature and reasonable assumptions, while those for ancillary structures are obtained through finite element analysis. Conventional and seismically isolated tunnels are selected for case studies. Results demonstrate that the resilience index effectively quantifies tunnel seismic resilience. Under frequent, design, and rare earthquake conditions, both tunnel types exhibit a high resilience state. Under the extremely rare earthquake condition, the seismically isolated tunnel exhibits superior resilience, outperforming the conventional tunnel. These findings validate the applicability and effectiveness of the resilience assessment framework.