Joint surface matching and shear strength part B: JRC-JMC shear strength criterion

When Barton's JRC-JCS shear strength criterion was used for the interpretation and prediction of shear strength of natural joints, it was found that the JRC-JCS model tends to overpredict the shear strength for those natural joints with less matched surfaces. To overcome this shortcoming, a new JRC-JMC shear strength criterion is proposed in order to include the effects of both joint surface roughness and joint matching, in the form of τ = σn·tan[JRC·JMC·log10 (JCS/σn) + r]. The JMC should be set at 0.3 for any measured JMC < 0.3. It is a modification of the existing JRC-JCS criterion. The new JRC-JMC model provides appropriate fitting of the shear test results on various joints with different degrees of surface, roughness and matching, and gives a better interpretation and prediction, particularly for natural joints that do not have perfectly matched surfaces.