A numerical study on offshore wind turbines embedded in sands

This paper compares the ultimate lateral capacity and stiffness of circular and square pile-towers embedded in two different sand deposits. The benefits of square pile-towers with respect to circular structures are brought out in this paper through a parametric study conducted by three dimensional finite element analyses. In the numerical models, the pile-towers are treated as an elastoplastic material while the soil is idealised using the Drucker-Prager constitutive model with a linearly increasing soil modulus. The effects of pile diameter, pile thickness, eccentricity and pile length for free-head pile-towers embedded in both sand deposits are investigated. The results illustrate that the stiffness and ultimate lateral capacity of a square pile-tower are substantially greater than a circular structure. Furthermore, the soil displacements and stresses at the ultimate capacity when a square pile-tower is adopted instead of circular structure are not considerable. The ultimate lateral capacities from the numerical models for both pile-tower configurations are compared with the usual techniques available in the literature, and the most suitable methods for these structures are illustrated, while the method adopted by Zhang et al. is ruled out.