Can Settle3D handle non-linear material?

Yes.  In Settle3D it is possible to define a non-linear material.  In a non-linear material, the modulus is not constant, but is a function of stress.  The graph below from section 3.2.2 of the Settle3D Theory Manual illustrates the relationship.

Settle3D-nonlinearsoil.PNG

Void Ratio vs log Vertical Effective Stress