Numerical investigation of soil parameter effects on the axial uplift bearing capacity of novel photovoltaic circular helicoid piles

The circular helicoid (CH) pile is a novel special-shaped pile developed over the past decade and widely used as an uplift-resistant foundation for photovoltaic support structures due to its superior uplift performance. However, the mechanisms by which ground conditions influence the mobilization of uplift bearing capacity remain unclear, limiting design optimization. In this study, a three-dimensional finite element model of CH pile foundations under axial uplift loading was established in ABAQUS and validated against seven sets of in-situ uplift load tests. Uplift bearing capacities were determined from the pile-head load-displacement response using the displacement control and double-tangent methods. Parametric and sensitivity analyses were performed to evaluate the effects of key soil parameters, including Young's modulus E, Poisson's ratio ν, cohesion c, internal friction angle φ, and the pile-soil interface friction coefficient µ. Results show that the uplift force-displacement relationship exhibits a smooth, progressive response, and the pile-head displacement at the ultimate limit state is approximately 0.1 times the pile diameter. Uplift bearing capacities increase positively with all considered parameters. The recommended parameter importance ranking is c > E > φ > ν > µ at the small-displacement stage, and c > φ > E > ν > µ at the large-displacement stage.