Shear strength criterion and shear components of rock joints I: Shear strength criterion

The peak shear strength of rock joints is influenced by both the surface morphology and the mechanical parameters of joint materials. In the existing references, special attention has been paid to the importance of roughness. Here, the importance of tensile strength of joint materials is discussed. The three-dimensional surface morphology along shear direction is captured by using the maximum potential contact area ratio, the maximum apparent inclination angle and the distribution of inclination angle. A new peak shear strength criterion is proposed, in which the dilatancy angle expressed by a hyperbolic function is used. A total of 85 sets of data are used to validate the criterion. The results show that there is good agreement between the calculated and measured values. 28 sets of data from natural rock joints are used to compare the new criterion and the famous JRC-JCS criterion. The discrepancy between the measured and calculated values by JRC-JCS criterion is something larger. The proposed criterion can be used as a predictive tool to evaluate the peak shear strength of rock joints owing to the fact that the roughness parameters can be easily obtained in the laboratory and the subjectivity can be avoided.