A Dynamic Risk Assessment Method for Deep-Buried Tunnels Based on a Bayesian Network

Table 4

Risk rating factors grading criteria.

	Factors	Grading
Objective factors	Section size	Medium			Large
	Construction method	Center diagram (CD) method	Bench cut method (BCM)	Ring cut method (RCM)	Full face excavation method (FFEM)	Center cross diagram (CRD) method
	Tunnel depth	<15 m		15~25 m	>25 m
	Surrounding rock level	IV		V	VI
	Groundwater	No water		Water leaking	Water gushing
	Mud inrush	No mud		Mud leaking	Mud inrush
Subjective factors	Prereinforcement effects	Good		Medium	Poor
	Support timing	In time			Late
	Construction quality	Good		Medium	Poor
	Construction experience	Well experienced		Medium	Inexperienced
	Construction management	Strict		Medium	Poor
	Support strength	High		Medium	Low
Monitoring factors	Inner-tunnel observation	Normal		Slight cracks	Slip off
	Arch crown convergence	III		II	I
	Side wall displacement	III		II	I