Barton - Bandis
The Barton-Bandis shear strength failure criterion for the rock mass takes the following form:
joint roughness coefficient
normal stress acting on the surface of the rock joint
joint compressive strength
basic angle of internal friction of the slip surface
If possible the shear strength parameters should be determined from in-situ measurements. Approximate ranges of parameters of the Barton-Bandis failure criterion are given here.