Effects of shearing direction on shear behaviour of rock joints

Effects of shearing direction on shear behaviour of rock joints were studied. Artificial triangular asperities with initial asperity angles of 9.5° (Type I) and 18.5° (Type II), inclined at 0°, 30°, and 60° from the direction perpendicular to the shearing movement were cast using high strength gypsum plaster. Samples were tested at different initial normal stress ranging from 0.56 MPa to 2.4 MPa under constant normal stiffness of 8 kN/mm. The measured data were analysed and accompanied by a mathematical model to describe the effects of shearing direction on shear strength of rock joints. The proposed model simulated reasonably the reduction in the shear strength of rock joints with increase in the angle of shearing direction.