Investigation on the Shear Behavior of Rough Rock Joints Prepared by Three- Dimensional Engraving Technique

Laboratory shear test is an important and widely used method to investigate the shear behavior of rock joints, and the preparation of joint specimens is a key factor that influences test results. In order to study the shear mechanism of rough rock joints with different morphologies in the laboratory, an innovative three-dimensional (3D) engraving technique was employed to produce specimens with rough joints. Intact sandstone and cement mortar blocks were used as model materials. The engraving parameters were determined to ensure a satisfactory engraving precision and to save as much time as possible for an engraving process. Three Barton profiles with joint roughness coefficient (JRC) values of 2.8, 10.8, and 18.7 were selected as the morphology prototypes for automatically engraving the model material blocks to obtain rough joint specimens. Shear tests were then conducted under four normal stress levels in the laboratory. In addition, numerical simulations on joints with the same physico-mechanical properties, surface morphology, and boundary conditions as the joint tested in the laboratory were performed. The failure characteristics, shear behavior curves, and shear strength obtained from numerical and experimental studies were analyzed considering the effect of joint materials, joint roughness, and applied normal stress. The shear mechanism of rough joints was investigated, and the analysis indicated that the results of shear tests by simulation and experiment were similar. The results revealed that it is feasible to make rough joints by engraving either real rocks or commonly used model materials (e.g., cement mortar).