Lateral Load Capacity of Helical Piles in Sand-Paper

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The study uses three-dimensional finite-element analysis in PLAXIS 3D to examine the lateral response of helical piles in sand. Piles with different shaft and helix diameters were modelled, along with conventional piles without helices. Analyses considered installation depths of 250–800 mm and sands with relative densities of 30% and 50%. Soil behaviour was represented by a Mohr–Coulomb model, and pile–soil interaction by interface elements.<br /><br />Results show that a helical blade can increase lateral load capacity and reduce pile deflection, particularly when the blade is relatively shallow. A larger helix generally provides greater resistance and reduces deflection, while the presence of a helix also lowers the maximum bending moment in the cases examined. Increasing sand density reduces lateral deformation but increases the maximum bending moment.<br /><br />Installation depth increases ultimate lateral capacity only up to a point. Using 5 mm of pile-head deflection to define ultimate load, the authors found that beyond an embedment ratio of roughly 15–18, the effects of helix diameter and additional depth become small. Soil-deformation contours likewise indicate that a deeply embedded helix may lie below the zone actively mobilised by lateral loading.<br /><br />The findings suggest that the lateral benefit of a helix depends on its position relative to the soil’s active deformation zone, rather than simply on its presence. They are based on numerical analyses calibrated against laboratory model tests, and the conclusions should be understood within the study’s model and soil conditions.

Keywords

helical piles

lateral response

PLAXIS 3D

finite-element analysis

sand

Mohr-Coulomb model

helix diameter

pile deflection

lateral load capacity

embedment ratio