Solution for strain-softening surrounding rock reinforced by grouted bolts

Abstract

To evaluate the reinforcement effectiveness of the grouted rock bolts, a dimensionless parameter’s approach (i.e. bolt density β ) is adopted. Following the Mohr–Coulomb and generalized Hoek–Brown failure criteria, the concept of the neutral point for the grouted rock bolts is introduced, and the determination of the equivalent plastic zone is divided into three categories (i.e. minimal yielding, major yielding, and excessive yielding). The potential plastic zone is sufficiently subdivided into a large number of concentric annuli through the finite difference approximation of equilibrium and compatibility equations. A simple approach for circular tunnel in strain-softening surrounding rock incorporating the neutral point of the grout rock bolts is proposed to derivate the solutions of stress and displacement. The proposed approach is validated with the published results. With the increase in bolt density β , the plastic radius would reduce 10%–30%, and the radial displacements would decrease by 10%–40%.