Three-Dimensional Finite-Element Modeling of True-Helix Piles in Sand under Axial Compression

The present study utilizes the coupled Eulerian–Lagrangian finite-element modeling technique to simulate three-dimensional piles with true helices in sand under axial compression. The aim is to develop a numerical methodology that accounts for installation-induced disturbances of the helices, evaluate the influence of the true-helix geometry, and investigate the axial failure mechanisms of helical piles in sand. The models include single-helix and double-helix piles with interhelix spacing ratios of 1.5 and 2.5. The results are validated against centrifuge model tests of helical piles in sand. The disintegration of axial loads between the helices and the shaft suggests higher loads in the helix in single-helix piles and lower helix loads in double-helix piles. The structural integrity of the helix, assessed against the ultimate axial load capacity, validates the assumption of elastic pile behavior and confirms its adequacy. The axial behavior of multihelix piles in sand was governed by an individual bearing mode (IBM). IBM failure also dominates for larger helix wings, while larger-diameter shafts lead to global failure, accompanied by ground surface heave. As pile embedment increases, the failure envelope around the upper helix of a double-helix pile transitions from a near-circular to a funnel-shaped pattern. A shaft-to-helix ratio of 1-to-3 presents an ideal selection for pile design.