Comprehensive Risk Evaluation in the Long-Term Operation of Urban Subway Based on Multiple Indices

Table 3

Risk grading for each factor.

Factor	Risk degree (score)
	Low	Moderate	High
	1	3	5
Maximum ground settlement (mm)	< 300	300–800	> 800
Maximum rate of ground settlement (mm/d)	< 0.08	0.08–0.14	> 0.14
Geological conditions	Hard formations	Soft formations	Mixed formations
Maximum settlement of tunnel (mm)	< 20	20–70	> 70
Lining leakage	No leakage	Partial leakage	Full leakage
Density of surface structures	Dense low-rise buildings	Dense moderate-rise buildings	Dense high-rise buildings
Disturbance of tunnelling (disturbed depth) (m)	< 0.8	0.8–1.5	> 1.5