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

Table 5

Criterion and quantitative standard of surrounding rock stability state.

No.	Conditions of the plastic zone	Stability of surrounding rock	Quantitative score
1	Communicated plastic zones occur in both joint planes and rock blocks	Unstable	1
2	Plastic zones occur in both joint planes and rock blocks, but only communicate in joint planes	Unstable	2
3	Communicated plastic zones only occur in joint planes	Unstable	3
4	Noncommunicated plastic zones occur in both joint planes and rock blocks	Stable	4
5	Noncommunicated plastic zones occur in joint planes	Stable	5
6	No plastic zones occur in both joint planes and rock blocks	Stable	6