Fig 1.
(a) Stress-strain curve of rock (b) Ideal stress-strain curve [5].
Fig 2.
Uniaxial experimental model of rock [5] and [13].
With the increase of axial pressure, the formation and development of horizontal cracks lead to the decrease of horizontal elastic modulus.
Fig 3.
The constitutive model, parameters A = 15 GPa, k0 = 0.1, C = 1, and εs = -0.1.
Fig 4.
Stress-strain curves of sandstone under the uniaxial compression.
(a) Lateral stress-strain curves. (b) Axial stress-strain curves.
Fig 5.
Elastic-plastic stress distribution diagram of thick-walled cylinder.
Fig 6.
Stress distributions along the cylinder radius (a) as A(ε) is not const. (b) as A(ε) is const. (c) A(ε) distributions along the cylinder radius as A(ε) is not const. Default values are r1 = 1 m, r2 = 10 m, P1 = 20 MPa, P2 = 0 MPa, E = 15 GPa, C = 1, εs = -0.1, and v = 0.1.
Fig 7.
The effects of constants on the stress distributions along the cylinder radius as A(ε) is not const.
Fig 8.
Distribution of stress around the tunnel.
The parameters for the proposed model and the Bray model with r1 = 1 m, r2 = 10 m, P1 = 20 MPa, P2 = 0 MPa, E = 15 GPa, C = 1, εs = -0.1, and v = 0.1.