Seismic vulnerability of deep tunnels influenced by chloride ion corrosion

Chloride ion erosion adversely affects the seismic performance of tunnels, making it essential to study the seismic vulnerability of tunnels in corrosive environments for a comprehensive seismic assessment over their entire lifecycle. To quantify the degradation trend in seismic performance of tunnels exposed to long-term chloride ion erosion, a seismic vulnerability analysis is conducted based on seismic vulnerability theory. A time-varying model accounting for the effects of chloride ion erosion on concrete and steel strength is employed. Peak ground acceleration and tunnel diameter deformation rate are selected as indicators for seismic intensity and structural damage, respectively. Through incremental dynamic analysis (IDA), the seismic vulnerability of deep tunnels is thoroughly investigated. Seismic vulnerability curves are obtained for various service periods and damage states. The results indicate that for the same service duration and seismic intensity, the probability of minor damage is the highest, followed by moderate and severe damage. For the same damage state and seismic intensity, as the service time increases, chloride ion erosion leads to a decline in tunnel seismic performance and a rise in damage probability. In the state of minor damage, when the peak ground acceleration is 0.30<italic>g</italic> and the service life reaches 100 years, the damage probability is 2.39 times higher than that in the initial service period. The research results provide a scientific basis for the seismic design of deep tunnels.