Study on the Mechanical Behavior of Double Primary Support of Soft Rock Tunnel under High Ground Stresses and Large Deformation

Table 1

Compressibility classification of the soft surrounding rock.

Classification		Strain (%)	Deformation description
I	0.4	1	Low
II	0.4∼0.2	1∼2.5	Medium
III	0.2∼0.15	2.5∼5	Severe
IV	0.15∼0.1	5∼10	Very severe
V	0.1	10∼15	Extremely severe