On the stress distribution at the bonding interface between rock and bolt

Abstract

Rock bolt is a major reinforcement technique for roadways in coal mines in China. Generally, separation of the bonding interface between the rock mass and the bolt may lead to collapse of the bolted rock mass due to stress concentration. In order to establish the stress concentration mechanism on the bonding interface, the distribution functions for shear stress and longitudinal force on the interface are derived using Mindlin's model, and a failure criterion for the interface is proposed. In addition, influencing factors for the stress distribution mode are identified. Both analytical study and numerical simulations by ANSYS have shown that, as the elastic modulus of rock increases, both shear stress and the longitudinal force-concentrating zone move towards the outer end of bolt and decrease gradually from the free surface to the rock mass body. Also, there is an optimizing cement thickness which results in relatively uniform distributions of shear stress and longitudinal force on the interface. It is valuable to investigate the bolt invalidity mechanism as well as reinforcement safety estimation in underground rock engineering design.

Keywords:

• rock bolt
• stress distribution
• bonding interface
• analytical model
• numerical method
• invalidity

Acknowledgements

This study was supported by the China Natural Science Fund (grant nos. 50534080 and 50674063), the Natural Science Fund of Shandong Province (grant no. Y2004F11), the Educational Department of Shandong Province, Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology (Project J06N04),e and Tai'shan Scholar Engineering Construction Fund, Shandong Province, China.