Rock-like materials generally manifest both strain-softening and pressure-dependent effects. The critical plastic strain corresponding to the residual state also increases with the confining pressure. In this case, all of the mechanical property parameters are the functions of plastic strain and confining pressure. The elastoplastic coupling strain-softening model (EPCSS) is established by dividing the elastic and plastic surrounding rock of circular openings into m and n annuli, respectively. When the range of each annulus is significantly small, the surrounding rock can be considered as isotropic and uniform. Then, the elastoplastic coupling analytical solutions can be derived by representing the material properties of each annulus with the corresponding value at each annulus’s outer radius for both Mohr–Coulomb (M-C) and Hoek–Brown (H-B) rock masses, respectively. Based on the continuum conditions of adjacent annuli, the equations for determining the radius of each annulus were established. Finally, the solutions were validated by strain-softening rock mass, and examples of EPCSS rock mass were further studied.

To understand the influence of temperature on the flow characteristics of fractured granite, high-temperature cyclic thermal treatment and flow tests on the fractured rock sample with different joint roughness coefficients and intact rock samples were conducted. The larger confining pressure and larger joint roughness coefficient will increase the resistance of fluid flow and affect the flow characteristics of the fluid. With the temperature increasing, the aperture of the fractures, the number of micro-fractures, and micropores increase which forms a large number of new connected hydraulic channels in the matrix. Forchheimer's law and Izbash equation can well describe the nonlinear flow characteristics, and the fitting coefficients are greater than 0.99. As the increasing temperature, the slope of the curve between the volumetric flow rate and pressure gradient gradually decreases, and the coefficients in Forchheimer's law and the Izbash equation decrease. The transmissivity decrease with the increasing Reynolds number and the change range of that increase with the increasing temperature. When the temperature is at the lower level (T = 200 ~ 600 °C), the contribution of split fracture to the permeability is greater than that of the matrix. When the temperature continuously increases to 800 °C, the contribution of the matrix to the permeability gradually rises and then exceeds that of split fracture. The results indicate that 400 °C is the critical temperature, after which the flow characteristics of fractured granite after high-temperature cycling change more obviously.

Considering the changes of permeability and Biot’s coefficients, the closed-form elastic-brittle-plastic solution of lined circular tunnels was proposed employing a Mohr-Coulomb non-associated flow rule. The influence of the reserved deformation of lining structure, permeability and Biot’s coefficients on the plastic radius, displacement and water inflow was studied. With an increase in permeability of the plastic region, the plastic radius and displacement decrease, and the water inflow increases. With an increase in Biot’s coefficient, the plastic radius, displacement and water inflow approximately increase in a linear way. The pore-water pressure in the surrounding rock increases with decreasing permeability of lining structure, and the water inflow has a contrary evolution. The increasing reversed displacement of lining structure increases the plastic radius, and lining structure reduces the water inflow but increases the pore-water pressure of the surrounding rock.

This paper deals with a spherical cavity excavated in infinite homogeneous and isotropic strain-softening rock mass subjected to a hydrostatic initial stresses. By simplifying the strain-softening process of the post-failure region as a Multi-step Brittle-Plastic model (MBPM), analytical solutions of the spherical cavity are derived with the consideration of the deterioration of elastic parameters. Meanwhile, critical deterioration conditions of elastic parameters are established theoretically. Both Mohr-Coulomb (M-C) and Hoek-Brown (H-B) criteria are included in the analysis. The results are compared with those obtained by former numerical methods, and the solutions are validated. Moreover, the presented results show that deteriorated elastic parameters for post-failure rock mass only has a little influence on stresses, softening radius and residual radius, but influences the deformation significantly.

To understand the influence of temperature on the flow characteristics of fractured granite, high-temperature cyclic thermal treatment and flow tests on the fractured rock sample and intact rock sample were conducted. With the temperature increasing, the aperture of the fractures, the number of micro-fractures, and micropores increase which forms a large number of new connected hydraulic channels in the matrix. Forchheimer's law and Izbash equation can well describe the nonlinear flow characteristics, and the fitting coefficients are greater than 0.99. As the increasing temperature, the slope of the curve between the volumetric flow rate and pressure gradient gradually decreases and the coefficients in Forchheimer's law and the Izbash equation decrease. The transmissivity decrease with the increasing Reynolds number and the change range of that increase with the increasing temperature. When the temperature is at the lower level (T = 200 ~ 600 ℃), the contribution of split fracture to the permeability is greater than that of the matrix. When the temperature continuously increases to 800 ℃, the contribution of the matrix to the permeability gradually rises and then exceeds that of split fracture. The results indicate that 400 ℃ is the critical temperature, after which the flow characteristics of fractured granite after high-temperature cycling change more obviously.