Modeling Soil lateral stiffness for single pile

[geolover]

Dear All

I want to model the single pile behavior under lateral load in soil media. how i can contribute soil horizontal stiffness in interaction properties?
I have select "hard contact" option in pressure-overclosure drop-down box for interaction properties of contact, at this case the result show no change in lateral soil deformation with changing in soil young modulus. so, i have decided to use linear stiffness instead. you can see attached file for more clarity.
your guidance would be highly appreciated.