Research on Failure Mechanism of Rockbolt Under Different Tensile–Shear Combination Loadings

This paper investigates the mechanical characteristics of rockbolt under combined tensile–shear loading conditions. By studying the stress and deformation throughout the elastic and plastic stages of rockbolt, a failure model for rockbolt under different tensile–shear combination loadings was established. Key parameters, including the maximum bending moment M_A and total plastic deformation λ, were identified and quantified as they evolve with changes in the displacement angle (combined tensile–shear state). The main novelty lies in formulating the key control parameters governing the elastic–plastic transition and failure process of rockbolts under combined tensile–shear loading and further incorporating them into FLAC^2D to improve the simulation of tensile–shear failure of rockbolts. Numerical simulations of rockbolts under combined tensile–shear loading were performed using FLAC^2D. The influence of a rock mass’ Young’s modulus and uniaxial compressive strength on the mechanical response of the rockbolt was investigated. The results indicate that the ultimate load-carrying capacity of the rockbolt remains essentially constant as the displacement angle increases, while the axial tensile force gradually decreases and the shear force gradually increases. The influence of a rock mass’ Young’s modulus on the stress–strain characteristics of the anchor exhibits a nonlinear positive correlation. When the uniaxial compressive strength of the rock mass is low, the rockbolt is prone to slippage during loading.