We need to model a concrete-bedrock interface for a shallow reinforced concrete foundation cast directly on rock.
We are assigning a Mohr-Coulomb material model specific to the interface elements representing the concrete-bedrock interface. The interface will be characterised by shear strength function of both friction and effective cohesion (resulting from the bond between concrete and bedrock) as well as a tensile capacity (equal to the tensile strength of the rock). These interface properties will be modelled using effective cohesion, friction angle and tension cut-off values.
In reality, when the interface is subject to shear stress, if the capacity is reached, the cohesion is lost and only the frictional component is left. Similarly, when the interface is subject to tension (due to a moment applied to the foundation for example), once the tension reaches the cut-off value, it should drop to zero as separation occurs between concrete and bedrock.
Is there a way to model this in PLAXIS? As it seems that in both cases, once shear capacity, or tension cut-off, are reached, then the values of cohesion and tension capacity don't drop to zero, but stay fixed at their limiting values.