PERFECT ELASTIC-BRITTLE-PLASTIC SOLUTION OF AXISYMMETRIC CIRCULAR OPENINGS IN ROCK MASS ON EXTENDED SMP CRITERION

Based on the extended Spatial Mobilization Plane Criterion (SMP), an elastic-brittle-plastic solution for an axisymmetric cylindrical tunnel was established, in which the influence of both intermediate principal compressive stress and material strain-softening behavior was considered, and the closed-form formulas of critical support force, the radius of a plastic zone, the distribution of stresses and displacements in surrounding rock were put forward. The elastic-plastic solution based on SMP was compared with Kastner solution, by which the rightness of the obtained elastic-plastic solution was verified. Also a comparative study between the elastic-brittle-plastic solution by obeying SMP and the current solution based on Mohr-Coulomb Criterion was made, including the examination of the influences of material strain-softening rate and intermediate principal stress. The results indicate that the rock strain-softening rate and the intermediate principal stress have a considerable effect on the stability analysis of surrounding rock, from which the strength potentials of rock mass can be used further, and it is also helpful for the design optimization of a tunnel support system.