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

Table 6

Discretized assessment index and description of tunnel collapse.

Damage level	Seismic damage description	Discrete value
Extremely severe	Collapse ( m^3); extensive and massive groundwater inrush; strong weathering or severe fractures of rock, extremely unstable collapse cavity; necessary measures should be taken immediately	4
Severe	Collapse (1000 m^3 <  m^3); local groundwater inflow; strong weathering or severe fractures of rock, unstable collapse cavity; necessary measures should be taken	3
Moderate	Collapse (300 m^3 <  m^3); local groundwater dripping; moderate weathering or a number of fractures of rock; poor stability of collapse cavity; measures should be taken as early as possible	2
Slight	Collapse ( m^3); local groundwater leakage or seepage; good stability of collapse cavity; slight weathering or few fractures of rock; measures should be taken in time	1
Undamaged	No collapse or groundwater; no abnormal phenomenon	0

Note:  = volume of tunnel collapse.