An analytical analysis for the mechanical performance of fully-grouted rockbolts based on the exponential softening model

Abstract

This paper presented a novel bond-slip model to better reveal the mechanical behavior of the bolt-grout interface for fully-grouted rockbolts under tensile loads by considering the non-linear response in the softening stage. The exponential decay function is adopted for describing the non-linear response in the softening stage. Based on the improved bond-slip model, the corresponding analytical solutions for the interfacial shear stress and the axial force of the bolt under different loading stages are solved. Then, the validity of this proposed model was verified by comparing with the experimental results. The results show that compared with the linear softening model, the proposed model is more suitable for predicting the mechanical performance of fully-grouted rockbolts. Finally, a series of parametric studies are conducted to explore the effect of model parameters on the mechanical properties of fully-grouted rockbolts. The results indicate that compared with the anchor length, the bolt diameter and the bond strength of the bolt-grout interface have a significance influence on the ultimate load of bolt, especially for the elastic and softening stage. Moreover, it can be found that using the linear softening model maybe overestimates the supporting performance of grouted bolt, resulting in an unsafe design for bolt.

Keywords

• Fully-grouted rockbolts
• Non-linear response
• Bond-slip model
• Anchor length
• Analytical solutions