A New Post-Seismic Damage Classification for Rock Tunnels Based on Analysis of 26 Global Earthquakes

Earthquakes such as Kobe, Chi-Chi, Wenchuan, and many more damaged the rock tunnels to various extents. To understand the vulnerability of rock tunnels caused by earthquakes, the damage degree and damage classification are major components. The damage degree and descriptions in the post-seismic damage classifications of rock tunnels are modified by researchers for every seismic event based on the amount of damage. This implies that existing post-seismic damage classifications are not uniform or consistent. The existing classifications are based on data from one or a maximum of three seismic events and also are site-specific, and lack a generalized view of the problem. To overcome such limitations, this study proposes a new post-seismic damage classification of rock tunnels. This classification is obtained from the largest global seismic damage database which contains information on 285 rock tunnels damaged by 26 earthquakes. This study introduces seven tunnel damage classes for different damage degrees namely None, Very Slight, Slight, Moderate, Severe, Extremely Severe, and Collapse with their detailed damage descriptions. Further, the influence of seismic, geological, and structural parameters are summarized from the database. The efficacy of this classification and conclusions from the influence parameters are validated by applying it to the five-rock tunnels damaged by Luding (2022), and Menyuan (2022) earthquakes in China and Kahramanmaraş earthquake sequences (2023) in Türkiye. The proposed classification shows a good agreement with the damage degree and its description for these five rock tunnels. Thus, the proposed damage classification and outcomes of influence parameters using such a large database can be utilized to understand the damage levels caused in the tunnel after an earthquake and for performing post-seismic damage assessment of rock tunnels.