A novel numerical-iterative-approach for strain-softening surrounding rock incorporating rockbolts effectiveness and hydraulic-mechanical coupling based on Three-Dimensional Hoek-Brown strength criterion

Abstract

The numerical solutions for strain-softening surrounding rock under 3D Hoek-Brown strength criterion are developed incorporating the influence of passive bolts and the seepage flow field. Based on 3D Hoek-Brown failure criterion, a numerical-increment-approach is reconstructed for the first time under the spatial axisymmetric conditions, in which the elastic and plastic zones are divided into a finite number of concentric annuli with constant increments of radial stress and radius between the adjacent annuli, respectively. Furthermore, the hydraulic-mechanical coupling model is improved by considering the effects of out-of-plane plastic strain and the spring-slider model is improved by considering the axial force at rockbolt head. On the basis of the reconstructed numerical-increment-approach and the improved spring-slider model, the bolt self-equilibrium conditions for five cases of passive bolts are also reconstructed (e.g., neutral point in elastic or plastic zones, neutral length in elastic, plastic or elastic-plastic zones, respectively). Ultimately, an improved numerical-iterative-approach is proposed in terms of the developed numerical-increment-approach and the reconstructed bolt self-equilibrium conditions, through which stresses and displacement of surrounding rock can be obtained by incorporating the effects of hydraulic-mechanical coupling and passive bolts. The corresponding calculation program is also presented. The reliability of the presented approach has been verified by the numerical and existed results. From a practical point of view, the proposed approach can be applied to estimate the reinforced ground response curves and optimize the length of passive bolts.