validation of pullout test

Hello Everyone !

I try to validate FEM pullout test of single bar by comparing results with test data.

I have performed laboratory pullout test, as a result getting test curve - relation.Force - Displacement 

I know internal friction angle of filling material and value of external pressure - in my opinion - this is

everything to compare results with predictions in PLAXIS 3D.

In Plaxis i have done a few models with different Rinter value.

I expected that some of FEM curves will be close to experimental ones

Unfortunately - the slopes of the FEM curves are the opposite that in experiment.

What could be the reason?

Regards!

Andrzej