Three-Dimensional Numerical Modelling of Load Distribution and Settlement of Pile Groups-Paper

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The paper evaluates a three-dimensional finite element method for predicting settlement and load distribution in pile foundations bearing in clay. The PLAXIS 3D model was calibrated against full-scale tests of a spread footing and a single pile, then applied to a 3-by-3 pile group. Predicted settlements and load transfer were compared with measurements and with the interaction-factor and equivalent-footing methods.<br /><br />The test foundations used 300 mm diameter, 5.5 m long piles in highly plastic, sensitive clay. The numerical model represented soil behavior as elastoplastic and included soil–pile interaction. It reproduced measured load–settlement behavior reasonably well, particularly under working loads. It also captured how loads were shared between the piles and the pile cap: most load was carried by the piles in the working-stress range, while the cap’s bearing reaction became more significant as pile loads approached failure.<br /><br />Both analytical settlement methods performed reasonably well at working loads. However, they underestimated settlement at higher loads, when foundation response became nonlinear. Interaction factors estimated from the tests agreed with analytical values at lower loads but increased substantially once nonlinear deformations developed. The equivalent-footing method likewise gave smaller-than-measured settlements beyond approximately 1,300 kN.<br /><br />The study concludes that three-dimensional finite element analysis can effectively model soil–structure interaction, pile-group settlement, and load transfer. The findings are limited to the tested soil conditions and pile type; additional studies are needed to establish their applicability elsewhere.

Keywords

finite element method

PLAXIS 3D

pile foundations

settlement prediction

load distribution

pile group

clay soil

soil-pile interaction

interaction factor

equivalent footing method