Shear Behavior of Rough Rock Joints Reinforced by Bolts

The shear response of rock joints under bolt reinforcement is important for supporting the design of a jointed rock mass. This paper aims to investigate the shear behavior of bolted rock joints with different roughness. Direct shear tests on both bolted and unbolted artificial joint specimens were conducted under various normal stresses. Before shear tests, three kinds of roughnesses for joints were created by split tests, and the roughnesses were quantitatively evaluated by a three-dimensional morphology scanner. After shear tests, the results showed that the bolt deformation decreased with increasing normal stress and increased with increasing roughness. Furthermore, the shear stiffness of the bolted joint specimens was, without exception, greater than that of unbolted specimens. Compared with those of unbolted specimens, the peak shear strength and the residual shear strength of bolted joint specimens with different roughnesses were improved to different degrees. Using the Coulomb failure criterion to linearly fit the shear strength and the applied normal stress, the equivalent cohesion and friction angle of the bolted joint specimens were found to have evident improvements compared with those of unbolted joint specimens. The increment rate of the equivalent cohesion of the bolted specimens increased with increasing roughness, whereas that of the equivalent friction angle decreased with increasing roughness.