The Jointed Rock model with overall Mohr-Coulomb failure criterion (Iso-JRMC) has been developed as a user-defined soil model. It is a combination of the Jointed Rock model (with isotropic elastic part) and the Mohr-Coulomb model. Plasticity will primarily occur in (up to) three stratification or fault directions (planes) using cohesion, friction angle, dilation angle and tensile strength on each plane, whilst an overall MC criterion (based on principal stresses) will be considered in all directions.
The advantage of this model over the standard Jointed Rock model in PLAXIS is that the latter may lead to 'locking' if a potential failure mechanism requires other than the predefined failure directions to develop. The Iso-JRMC model will overcome the 'locking' since it may (eventually) fail in other directions as well (according to the overall Mohr-Coulomb criterion), such that a continuous failure mechanism may be obtained.
A limitation of the Iso-JRMC model is that the elastic behaviour is isotropic.
With the release of PLAXIS 2D/3D CONNECT Edition V20 Update 1 (January 2020), the PLAXIS User Defined Soil models are delivered with the PLAXIS installation. When enabling the Geotechnical SELECT Entitlement [GSE] when starting the PLAXIS application, this model becomes available in the Parameters tab when selecting "User defined" for the Material model.