Analysis on Loose Circle of Surrounding Rock of Large Deformation Soft-Rock Tunnel

Table 2

Classification standard for large deformation of soft rock.

Surrounding rock classification	I	II	III
Strength-stress ratio ()	0.5∼0.25	0.15∼0.25	<0.15
Deformation amount (cm)	20∼40	40∼60	>60
Large deformation degree	Slightly large deformation	Medium-large deformation	Severe large deformation