Rapid Assessment and Classification for Seismic Damage of Mountain Tunnel Based on Concentric Circle Method

Table 2

Relationship between seismic damage index and seismic damage level of tunnel.

Level	Extremely severe	Severe	Moderate	Slight	Undamaged
Index	= 1	9/16 <  < 1	4/16 <  < 9/16	1/16 <  < 4/16	0  < 1/16

Standard value of 0, 1/16, 4/16, 9/16, and 1 is the area ratio of the concentric circles with different radius (0, 1, 2, 3, and 4) to the largest concentric circle with radius 4.