Stress Analysis of Full-length Bond Bolt Under Shear Deformation of Anchor Interface

Bolt anchoring force is closely related to the shear properties of the anchor interface. Considering the shear properties of anchoring agent and contact interface bonding behavior, the shear stress distribution of full-length bond bolt is analyzed based on the stress-strain relationship among bolt, anchoring agent, surrounding rock and bond interface. In this case, both the interface shear stress of the anchoring agent, surrounding rock and the bolt axial force is obtained respectively under drawing and actual working conditions. The results show that the peak shear stress of the interface, including the shear deformation of the contact interface, is significantly lower than that without it when the drawing force is applied. When designing the bolt parameters under the actual working conditions of grade IV and V surrounding rock, the relative deformation between surrounding rock and anchor should be considered, and the distribution of shear stress changes from “unimodal” to “bimodal ”. In the case of a lower elastic modulus of surrounding rock, both the shear stress concentration and distribution range are obvious, and the position of the neutral point is near the orifice. With the increase of elastic modulus, both the shear stress concentration and distribution range are reduced, and the position of the neutral point moves towards the depth of bolt. As a result, the optimum bolt length of full-length bond bolt can be determined by field test and decreases with the increase of elastic modulus of surrounding rock.