Investigation of Shear Mechanical Behavior and Slip Weakening Characteristics of Rough Joints in Rock Mass

The surface morphology of a structural plane is an important factor affecting the shear mechanical behavior of a structural plane. A direct shear test of a rough structural plane is carried out, and the shear mechanical behavior and slip weakening characteristics of a structural plane under different levels of roughness and normal stress conditions are studied; the normal stress conditions ranged from 2 MPa to 14 MPa. The results show that the shear strength and shear stress drop of a rough structure increase as the normal stress and roughness levels also increase. The higher the roughness level, or the greater the normal stress level, the more elastic energy the structural plane accumulates before shear failure. Once the shear stress is great enough and shear failure occurs, the shear slip of the rough structural plane shows obvious stick slip characteristics, and it releases more energy. Under high normal stress conditions, the convex body of the structural plane is damaged earlier in the process of direct shear, and the duration of convex body damage and failure is longer. After direct shear, the roughness of the structural plane decreases exponentially as normal stress levels increase. The shear slip of the structural plane, which has a significant degree of roughness under high normal stress conditions, shows a significant number of slip weakening characteristics, which is the main reason that the stick slip of the structural plane releases a lot of energy.