A New Unified Solution for Circular Tunnel Based on a Four-Stage Constitutive Model considering the Intermediate Principal Stress

Table 1

Geometrical and physical parameters of the circular tunnel.

Parameters	Values from Pan’s research [23]
Radius of the opening, (m)	10
Initial stress, (MPa)	30
Internal pressure, (MPa)	0
Young’s modulus, (MPa)	2000
Dilation coefficient,	3.0
Poisson’s ratio,	0.3
Initial cohesion, (MPa)	6
Residual cohesion, (MPa)	6
Strain-softening factor, (MPa)	0
Internal friction angle, (°)	30