Study on Identification of Construction Method for Ultra-Large-Span Tunnel

Table 10

Index value and qualitative description of tunnel stability.

F	Unstable state			Stable state
	<13	[13, 17)	[17, 23)	[23, 26)	[26, 40)	≥40
Description of stability	Extremely unstable	Very unstable	Unstable	Basically stable	Very stable	Highly stable