Study on Disease Mechanism and Theoretical Quantification Method of Tunnel Structure

Table 4

Evaluation criteria for failure to determine whether cracks develop.

Crack width b (mm)			Crack length l (m)			Rating status
b > 5	5 ≥ b > 3	3 ≥ b	l > 10	10 ≥ l > 5	5 ≥ l
✓			✓			3/4
✓				✓		2/3
✓					✓	2/3
	✓		✓			3
	✓			✓		2/3
	✓				✓	2
		✓	✓	✓	✓	1/2