Designing Piled Foundations with a Full 3D Model

Background:

The analysis of piled foundations, where horizontal environmental loads play a very important role, has taken foundation design a step further in the 1970s and 80s. Nonlinear analyses considering P-y, T-z and Q-z curves became the state-of-the-art which also included group effect calculations thanks to an approximation proposed by [1] on the [2] equations. For some reason, however, foundation design continued to be refined using finite element calculations, but the corresponding developments never made their way into the main offshore platform design codes such as [3,4].

Objective:

Considering the enormous advantage that this brings for topics such as group effect and negative friction, it is obvious that opening the offshore market to this enhancement is totally desirable. This is exactly what this paper is trying to achieve.

Method:

In order to increase the accuracy of the prediction of piled foundations lateral displacements when group effect is considerable, a complete 3D model will be proposed using the finite element method and compared to the codes’ model and also experimental data.

Results:

The model in DIANA showed good performance in comparison to the codes’ model and experimental data for the single pile. When the pile group model, when the codes’ have known deficiencies, was tested, both efforts on each pile and mean displacement of the pile group fit the experimental data. However, the behavior of each pile of the group, if separately analyzed, didn’t fit many experimental data, which was attributed to the soil model utilized.

Conclusion:

This improved modeling procedure has been proven to improve the lateral displacement prediction of a piled foundation when group effect is considerable, when compared to codes [3,4] proposed models. However, the study of more accurate soil models could help on achieving more realistic results.

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