A Rock Mass Classification Method for Tuff Tunnel Based on the High-Pressure Gas Expansion Method

Table 3

Relationship between and the degree of rock integrity.

	Degree of rock integrity
>0.75	Intact
0.75∼0.55	Relatively intact
0.55∼0.35	Relatively crushed
0.35∼0.15	Crushed
≤0.15	Extremely crushed