Effect of Cyclic Shear Loading on Shear Performance of Rock Bolt Under Different Joint Roughness

The mechanical and deformation properties of bolted joints are important research issues in rock mechanics and rock engineering. Quite a few tests have been performed to study the performance of rock bolts in resisting shear loading. The effect of cyclic shear loadings on the bolts in the joints under different joint roughness was studied through a series of shear tests. The results illustrate that the peak shear strength was substantially equal to the residual strength with the increase in the number of cycles, and the slope of the normal displacement curve gradually decreased. When the number of shears is greater than three, the shear stress curve and the slope of the normal displacement curve tend to be stable gradually, which means it has completed the asperity degradation. The cyclic shear loading affects the rock bolt and reduces its bearing capacity. For specimens with larger JRC, the peak shear stress in both the direct shear and the first cycle was significantly elevated compared with small JRC, and so was the normal displacement. An evaluation index of shear energy loss ratio (SELR) was introduced to evaluate the shear performance of the rock bolts and rock joints under a cyclic shear loading condition. When the JRC is large enough, the asperities are difficult to degrade, and the jointed rock still has a more remarkable ability to resist shear deformation. This shows that JRC significantly affects the performance of joint plane and rock bolts under cyclic shear loading.