A semi-analytical procedure for circular opening in strain-softening rock masses

A semi-analytical procedure is introduced to solve the stress and displacement distributions of strain-softening rock masses surrounding a circular opening on basis of Hoek-Brown failure criterion. The numerical solution and closed-form solution are obtained for plastic softening and residual zones, respectively. The critical support pressures for the plastic softening and residual zones are investigated. The displacements at the opening boundary, radii of plastic softening and residual zones with different critical values of plastic shear strain (i.e. critical plastic parameters) and different dilatancy angles are predicted. The result indicates that as the critical plastic parameter grows, radial displacement becomes less affected by the dilatancy behaviours of rock mass. Dilatancy property has trivial effect on the radii of the plastic softening zone and residual zone when the value of critical plastic parameter is marginal or great.