Unified solutions for stresses and displacements around circular tunnels using the Unified Strength Theory

The unified solutions are presented for stresses and displacements around a circular tunnel subjected to a hydrostatic stress field. The rock mass is assumed to be elastic-brittle-plastic and governed by the Unified Strength Theory. The displacements are obtained accounting for three different definitions for elastic strains and different Young’s modulus in the plastic zone. The unified solutions obtained in this paper are especially versatile in reflecting the intermediate principal stress effect to different extents for different materials. The conventional solutions, based on the Mohr-Coulomb failure criterion and the Generalized Twin Shear Stress yield criterion, are special cases of the present unified solutions. The new unified solutions can compare with those computed by the latest generalized Hoek-Brown failure criterion. The results obtained demonstrate the importance of the intermediate principal stress influence for the stresses and displacements analysis. The effects of different definitions for elastic strains and different Young’s modulus in the plastic zone on the displacements are significant.