Elastoplastic Coupling Solution of Circular Openings in Strain-Softening Rock Mass Considering Pressure-Dependent Effect

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.