Shear Stress Distribution of Fully Grouted Rockbolts under Tensile Loads

Abstract

Bolt is a safe and dependable engineering anchoring technique, and the stress transfer mechanism of the bolt has been the subject of research. Based on the bolt–grout interface deformation coordination relationship, this paper establishes physical equations using the Mindlin displacement solution and deduces the theoretical distribution of shear stress along the anchor length for fully grouted bolts. This paper also conducts an indoor bolt pullout test to verify the accuracy of the calculation results. The results show that when the bolt is subjected to tensile load, the shear stress shows a tendency to increase sharply and then decrease slowly. As the load increases, the shear stress also increases, with the extreme points gradually moving away from the pullout end. The distribution of shear stress is also directly related to the anchor length and diameter. By controlling the ratio of these two parameters, the shear stress on the bolt can be reduced by 50%–70%. Meanwhile, the ratio of the elastic modulus of the rock mass Ec to the elastic modulus of the bolt Es, Ec/Es, has a significant effect on the distribution of shear stress. The shear stress model established in this paper matches well with the experimental data, with a fitting coefficient R2 ≥ 0.9, which demonstrates high accuracy and applicability. In engineering practice, by taking into account the specific conditions of the construction site, the model developed in this study can be utilized to choose bolts of suitable size, thereby optimizing anchorage efficiency.