Recently, I have investigated the behavior of the multi-helix piles in terms of both capacity and failure mechanism embedded in the sandy soil under uplift loading in PLAXIS 3D. For modeling the pile, the plate element has been employed in the analysis. However, the second helix in the model I have installed cannot run effectively. It is obtained that the capacity of a double-helix pile is lower than a single-helix pile. Also, the pile element has been modeled as volume. However, the results did not change, and it is seen no contribution of the second helix to the uplift capacity. On the other hand, I have investigated in my previous work the compression behavior of the multi-helix piles embedded in the sand with small and large-scale experiments to compare the numerical analyses. According to the results, the findings of experiments and numerical analyses were quite compatible. What is the reason for the second helix not running effectively in uplift loading?
Dear Buse,
As you can imagine it is very difficult to comment on modelling such a complex 3D case in the forum without any details on how it looks or checking the results.
In your post, you mention that you get a much lower capacity with the double helix, but the main question is how do you compute the capacity? If it is by running a plastic analysis and seeing when it fails (and stops) then maybe you need to check for a local failure that is more of numerical origin rather than realistic and can be bypassed somehow.
Later in your post you mention that "according to the results, the findings of experiments and numerical analyses were quite compatible." Does that mean that the physical experiments are in agreement with the numerical results? Then, maybe the answer should not be necessarily investigated on a numerical tool but on the actual structural and soil behaviour.
I noticed that you created a service request, too, so I can dive in a bit more into this interesting case.
Answer Verified By: Buse Emirler
Thank you for your interest.