Shear mechanics and acoustic emission characteristics of penetrating standard JRC double joints

The anti-shear performance of rock joints is a significant factor that affects the strength and stability of engineering rock mass. In this study, the standard joint surface mold and fixed splints are produced based on the 3D printing technology, and the double-joint specimens with different joint spacings and roughnesses are prepared by adopting the integrated pouring method, and then the acoustic emission technology is combined to explore the shear mechanical properties and failure evolution characteristics of the rough double-joint rock mass under different normal stress conditions. The results indicate that the patterns of shear stress displacement curves are affected by the joint roughness and normal stress. With the increase of the JRC and normal stress, the degree of softening of the shear stress increases; when the normal stress is larger, there are multiple sudden drops in the shear stress at the post-peak stage, and the sudden descending value increases with the normal stress. The peak shear intensity appeares at the fracture of the rock sandwich between two joints, showing an increasing trend with the increase of the JRC and normal stress and decreasing with the increase of the joint spacing. The AE results show that the AE energy increases sharply at the fracture moment of the interlayer, and the peak value of AE energy slightly lags behind the peak value of shear stress. With the increase of the normal stress, the peak value of AE energy and the cumulative AE energy value increase. The AE positioning points are concentrated in the rock interlayer, occurring frequently within the range of 200~600 s, and with the increase of the joint spacing, the concentration range of the AE positioning point expands.