I haven't done any research on how friction is used in pile/soil models, but I can give you my thoughts. A coefficient of friction creates a frictional force because there is a normal force at the interface. What is the normal force that the soil makes against the pile? However, even if there is a large normal force, the soil has a limited shear strength, so the frictional force can't be greater than the shear strength.
I don't often use Elastic Support in Ansys Mechanical, but my understanding is that it only provides a spring force normal to the surface. When the surface is a vertical cylinder, it will provide a lateral stiffness that opposes motion in the ground plane, but does it provide any stiffness in the vertical direction? What happens when you run the model with elastic support and a Standard Earth Gravity load? How far does the structure sink into the ground? From the weight of the structure, you can calculate the vertical stiffness.
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