Increase of stiffness in the Mohr-Coulomb Material Model

Hi all,

I am running into trouble with the increase of stiffness in the Mohr-Coulomb Material Model. 

The increase in stiffness in the Model is linear, while my stiffness is parabolic. Is there a way to adapt a parabolic change into the Mohr-Coulomb Model or is there a Material Model where the stiffness can change in parabolically over the depth?

Thank you for your time

Jesco