ABAQUS Analysis

How to differentiate between the analysis of a "hollow pile with closed top and an open end" with "vented top and open ended pile".

After applying compressive load at both the pile tops (closed and vented), i have obtained/observed that the vented pile is offering higher resistance to penetration as compared to closed top pile.

 The sequence of steps i have followed are Geostatic, Contact and Compressive loading respectively. How to Model/Analyze the hollow pile with vented top so that it offers lesser resistance as compared to hollow pile with Closed top.

Mohr-Coulomb plasticity model has been considered for soil and concrete is taken as pile material. 3D stress element is choosen for both the soil and pile.

Thanking you,  

 Tanmoy Kr. Deb