Modeling and analysis of the effect of helix geometry on the uplift capacity of helical anchors for floating offshore wind applications using the material point method

Helical anchors have emerged as promising anchor solutions for floating offshore wind turbines in deep waters. Previous studies on helical anchors exhibiting large deformations have predominantly relied on continuum-based numerical approaches, often invoking simplified assumptions about failure mechanisms. Influence of multiple-helix configurations on uplift capacity remains insufficiently understood. In this study, the uplift behavior of helical piles embedded in medium-dense to dense sand is investigated using the Material Point Method (MPM). Particular emphasis is placed on quantifying the influence of anchor geometry and soil density on pull-out resistance and the associated failure mechanisms. Anchor–seabed interaction is simulated using representative pile geometries, where the influence of installation on the surrounding soil is represented through simplified modification of the initial effective stress for the pile–soil configurations considered. An elasto-plastic constitutive framework with multiple hardening rules is incorporated to simulate the nonlinear stress–strain relationship of sand. The numerical model is validated against centrifuge tests of two helical anchor configurations. A comprehensive parametric study is performed for the impact of key geometric variables; the number of helices, helix spacing, and helix diameter; on the uplift capacity and load–displacement response. The results reveal that, while the predicted uplift capacity factors for single-helix anchors are consistent with experimental and analytical data, the multi-helix predictions exhibit clear deviations from established formulations, particularly at larger helix spacing ratios. These findings highlight that the uplift response of multi-helix anchors is primarily controlled by helix–helix interaction and load redistribution between the upper and lower plates. This, in turn, alters the governing failure mechanisms beyond the assumptions embedded in conventional approaches. Therefore, a contribution-weighted bearing-capacity normalization is proposed to account for multi-helix interactions. The study demonstrates the MPM’s capability to simulate large-deformation seabed–helical anchor interactions and provides a basis for future investigations that explicitly incorporate installation effects.