Damage Assessment of Tunnels in Seismic Prone Zone During Earthquakes: A Part of Hazard Evaluation

Tunnels are generally constructed in urban areas and metro cities to fulfill the rising need of space and passage due to urbanization. These infrastructure may get damaged because of earthquakes occurring in that particular area where tunnels are constructed. While designing tunnels in seismic prone zones, it is ensured that tunnels must withstand under both seismic and static loading. Recently occurred large magnitude earthquakes caused significant damages of the tunnels including the 1995 Kobe earthquake in Japan, the 1999 Chi-Chi earthquake in Taiwan and the 2008 Wenchuan earthquake in China. During damage evaluation, tunnel damages are broadly categorized into five classes based on damage index including no damage, minor damage, moderate damage, major damage and collapse. This paper gathers the materials of tunnels affected by the 1995 Kobe earthquake in Japan and the 1999 Chi-Chi earthquake in Taiwan, and the grades of damage are calculated based on seismic performance. Earthquake intensity, distance from fault, rock classification, tunnel length and overburden depth are considered as the tunnel damage factors while doing analysis. Considering these parameters, the formula for seismic damage evaluation for tunnel is deducted using the least square method. Further, this formula is modified after taking into account additional factors like construction time, seismic fortification strength and portal stability.