Barton-Bandis
The Barton-Bandis strength model can be used to model the shear strength of a joint. The Barton-Bandis strength model establishes the shear strength of a failure plane as:
where is the residual friction angle of the failure surface [Barton and Choubey, 1977],
JRC is the joint roughness coefficient, and JCS is the joint wall compressive strength.
For further information on the shear strength of discontinuities, including a discussion of the Barton-Bandis failure criterion parameters, see Chapter 4 of Practical Rock Engineering by Dr. Evert Hoek, available on the Rocscience website.