Failure behavior and strength model of blocky rock mass with and without rockbolts

Abstract

To better understand the failure behaviours and strength of bolt-reinforced blocky rocks, large scale extensive laboratory experiments are carried out on blocky rock-like specimens with and without rockbolt reinforcement. The results show that both shear failure and tensile failure along joint surfaces are observed but the shear failure is a main controlling factor for the peak strength of the rock mass with and without rockbolts. The rockbolts are necked and shear deformation simultaneously happens in bolt‑reinforced rock specimens. As the joint dip angle increases, the joint shear failure becomes more dominant. The number of rockbolts has a significant impact on the peak strain and uniaxial compressive strength (UCS), but little influence on the deformation modulus of the rock mass. Using the Winkler beam model to represent the rockbolt behaviours, an analytical model for the prediction of the strength of bolt-reinforced blocky rocks is proposed. Good agreement between the UCS values predicted by proposed model and obtained from experiments suggest an encouraging performance of the proposed model. In addition, the performance of the proposed model is further assessed using published results in the literature, indicating the proposed model can be used effectively in the prediction of UCS of bolt-reinforced blocky rocks.

Keywords

• Blocky rock mass
• Rockbolt ground support
• Uniaxial compression test
• Failure mechanism
• Uniaxial compressive strength model