An Improved Analytical Model for the Elastic and Plastic Strain-hardening Shear Behaviour of Fully Grouted Rockbolts

Fully grouted rock bolts are one of the main forms of rock reinforcement used in underground mines, especially in coal mines. Analytical models describing the deformation behaviour of rock bolts under various loading conditions are used in numerical models for designing appropriate rock reinforcement. A reliable analytical model capable of accurately predicting rock bolts’ responses under different loading conditions is, therefore, important for more realistic numerical models and effective reinforcement design. In this paper, a new analytical model for shear behaviour of rock bolts is proposed which can better predict rock bolt behaviour under large shear deformations. A method to consider the effect of post-elastic strain hardening on bending stiffness of rock bolt is presented. The analytical model is validated with results from laboratory shear tests and found to be consistent with the laboratory results. To analyse the effect of post-elastic strain hardening on shear behaviour of a rock bolt, results from the proposed analytical model is compared with analytical model without strain-hardening effect. Without strain hardening, the analytical models overestimate the ultimate shear displacement by up to 35% in the examples shown in the paper.