Study on Mechanical Effect and Plastic Zone Distribution of Tunnel Surrounding Rock in the Presence of Various Expansion Approaches

Table 1

Mechanical parameters of the surrounding rock.

Material	Modulus of elasticity; (E (GPa))	Poisson ratio; (μ)	Density; (kN/m³)	Angle of internal friction (degree)	Cohesive force; (MPa)
Class III surrounding rock	10.7	0.28	24	44	1.1
Class IV surrounding rock	5.5	0.32	22	30	0.3
Class V surrounding rock	1.1	0.4	18	25	0.1
Mix by spraying	25	0.2	—	—	—
Anchor	210	0.3	—	—	—
Second lining	31	0.2	—	—	—