Investigation on the interaction mechanism and failure behavior between bolt and rock-like mass

Abstract

The matching relationship between bolt diameter and borehole diameter determines the bolt supporting effect in the mining roadway. In this paper, the failure modes of the anchorage body under different diameter matching were studied by the pullout test. When the anchorage agent was pulled out completely with bolt, the anchoring effect was ideal. Whereas, when the bolt was pulled out smoothly with only a thin layer of anchorage agent, the anchoring effect was relatively worse. Through multiple pullout tests, the suitable diameter matching difference can be defined with a range of 6–11 mm. Based on the interface sliding failure mode between anchorage agent and rock-like mass, a mechanical model of diameter matching was established. Both equations of tensile force and interfacial shear stress along with the anchorage direction in perfectly elastic state were derived. FLAC 3D was applied to analyze the distribution of interfacial shear stress and axial stress under different diameter matching between the bolt and the borehole. As a result, a 4–11 mm diameter difference shows the best anchoring effect. According to both experimental and simulation results, the optimal diameter matching difference is 6–11 mm.