“…where JRC is the joint roughness coefficient, JSC is the joint compressive strength, φ r is the residual friction angle, and σ n is the normal stress. The JRC and JSC indexes are popularly known (see [2,5,6,8,11,12,18,20,22,26,27] for example). However, the JRC index (first proposed in [6]) is the most problematic term in present; the methods of its estimation are based on the empirical analysis of fracture curves -Barton roughness profiles.…”