Influence of seismicity level on seismic tunnel damage evolution and design implications: A multi-regional comparison

초록

This study presents a comprehensive cross-regional assessment of seismic performance, fragility behavior, and post-earthquake functionality of circular tunnels located in three distinct seismotectonic environments: lowmoderate seismicity in Oman, moderate seismicity in South Korea, and high seismicity in the Himalayan region. A unified analytical framework integrating ground-structure interaction, lining response, damage index evaluation, probabilistic fragility modelling, and network-level functionality analysis was developed to enable a consistent comparison across regions. Results revealed a clear escalation in seismic demand and tunnel vulnerability from Oman to South Korea and the Himalayas, governed respectively by P-wave-dominated deformation, soil amplification and liquefaction effects, and brittle rock-mass behavior under high PGA. Fragility curves indicated that the onset of moderate and extensive damage shifts toward significantly lower intensities in the Himalayan region, while South Korea exhibited zone-dependent sensitivity driven by microzonation and ground-modulus degradation. Post-seismic functionality analysis further showed that Oman tunnel remains fully operational, South Korean tunnels experience partial service reduction, and Himalayan tunnels approach neartotal operational loss even at moderate shaking. Quantitatively, the composite vulnerability score increased from 0.18 in Oman to 0.59 in South Korea and 0.92 in the Himalayan region, while failure probability at representative regional PGA rose from less than 12% to nearly 90%. The results further indicate that Himalayan tunnels require approximately 25-35% higher effective lining stiffness and enhanced confinement detailing compared to low-moderate seismicity environments to maintain comparable safety margins. The integrated findings offer critical engineering implications for region-specific seismic design, resilience-based retrofitting, and transportation network planning, establishing a robust framework for enhancing tunnel safety in diverse seismic environments.

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