Uncertainty Analysis on Risk Assessment of Water Inrush in Karst Tunnels

Table 1

Indices and criteria for risk assessment of water inrush in karst tunnels.

Indices for risk assessment of water inrush	Risk grade
	IV	III	II	I
Formation lithology	0~4.2	4.2~10.4	10.4~25.4	>25.4
Unfavorable geological conditions	<60	60~70	70~85	85~100
Groundwater level	<10	10~30	30~60	>60
Landform and physiognomy (proportion of negative landform area)	<20	20~40	40~60	>60
Modified strata inclination	0~5	5~10	10~25	25~45
Contact zones of dissolvable and insoluble rock	<60	60~70	70~85	85~100
Layer and interlayer fissures	<60	60~70	70~85	85~100