The role of dynamic normal disturbances on shear properties and failure behaviours of bolt anchorage systems

This study investigates the mechanical properties and damage mechanisms of bolt-resin-rock anchorage systems subjected to shear under dynamic normal disturbances. The effects of initial normal load F_nd, cyclic normal amplitude f_a, cyclic normal frequency f, and shear rate v on the shear load, normal displacement, wear characteristics and strain evolution are analysed. The test results show that the peak shear load decreases by 7.82 % ∼ 28.95 % with increasing f_a, whereas it increases linearly by 15.77 % ∼ 79.85 % with F_nd. The load bearing capacity of the anchorage system is significantly weakened with increasing f, but is not sensitive to the changes of v. The system undergoes shear-induced consolidation and exhibits normal shear contraction during the initial shearing stage. As shearing progresses, the developing penetration plane enhances the climbing effect, leading to pronounced normal dilation. The resin-rock interface is more prone to debonding failure under intensified normal disturbances, whereas the shear penetration surface forms at the bolt-resin interface under high-frequency but low-amplitude normal disturbances. The force chain evolution characteristics of the anchorage system under dynamic normal disturbances from a mesoscopic perspective are analysed via the particle flow numerical simulation method from 3D point, including interface shear force distribution, cracks propagation patterns, and debonding failure mechanisms.