Anchorage Mechanical Effects of Tunnel Surrounding Rock by Considering Post-Peak Characteristics

Abstract

This work aims to study the mechanical mechanism of the post-peak tunnel surrounding rock state under grouted bolting support. The post-peak surrounding rock, which is under the effect of secondary stress from the free surface to the deep tunnel, can be divided into the residual strength, plastic softening, and elastic deformation zones according to the mechanical characteristic. The bolt axial stress and shear strength equations are obtained based on the principle of bolt bonding resistance to sliding deformation. The supporting force, which is provided by the grouted rock bolt through the rock-anchorage face, is assumed to be equivalent to the radial body force of the surrounding rock. Therefore, the balance equation is established by considering the influence of bolting support. The radii of the post-peak residual and softening zones, as well as the displacement and stress under grouted bolting support, is determined by combining the compatibility equations of the residual and softening plastic zones and considering rock post-peak strain softening and dilatancy with the balance equation. On the basis of theoretical research cases, the reinforcement effects between the grouting anchor and the surrounding rock, as well as bolting pretension, significantly improve the mechanical properties of the softening and dilatancy characteristics and control the development of the regional range and deformation of the surrounding rock.