Seismic damage to non-fault-crossing and fault-crossing tunnels: Comparative study of the 2008 Wenchuan earthquake (Mw 7.9) and the 2022 Menyuan earthquake (Mw 6.7)

In regions with complex geological environments, tunnel projects are highly susceptible to severe damage during strong earthquakes, posing significant challenges for the construction and operation of essential lifeline projects. Therefore, it is crucial to understand the dynamic response of tunnels under strong earthquakes. This study focused on the severe damage caused to multiple highway and high-speed railway tunnels by the 2008 Wenchuan Mw7.9 earthquake and the 2022 Menyuan Mw6.7 earthquake. Based on the damage characteristics, the damage types of highway tunnels and high-speed railway tunnels were classified into five typical types: lining cracks, lining spalling and collapse, construction joint damage, pavement or bottom structure damage, and water leakage. By considering the characteristics of near-fault seismic motions, such as pulse, energy, and time-frequency, as well as fault properties and geological conditions, a comparative analysis and mechanism study were conducted to emphasize distinctions between fault-crossing and non-fault-crossing tunnels, as well as the influence of seismogenic faults on tunnel damage. The importance of the combined effects of transient displacement and the release of strong seismic motions from seismogenic faults on damage to fault-crossing tunnels was emphasized. Moreover, based on the relationship between the degree of damage and the distance from the fault zone in fault-crossing tunnels, a five-segment damage zoning method was proposed, including the fault-crossing section, near-fault section, fault-affected section, portal-affected section, and conventional section. Through this study of the actual seismic damage characteristics and mechanisms of tunnels, valuable insights are provided for improving the resilience of lifeline tunnel projects.