Numerical Analysis of Large-Diameter Monopiles in Dense Sand Supporting Offshore Wind Turbines

Large-diameter monopiles are widely used foundations for offshore wind turbines. In the present study, three-dimensional finite-element (FE) analyses are performed to estimate the static lateral load-carrying capacity of monopiles in dense sand subjected to eccentric loading. A modified Mohr-Coulomb (MMC) model that considers prepeak hardening, postpeak softening, and the effects of mean effective stress and relative density on stress-strain behavior of dense sand is adopted in the FE analysis. FE analyses are also performed with the Mohr-Coulomb (MC) model. The load-displacement behavior observed in model tests can be simulated better with the MMC model than with the MC model. On the basis of a parametric study for different length-to-diameter ratios of the pile, load-moment capacity interaction diagrams were developed for different degrees of rotation. A simplified model, based on the concept of lateral pressure distribution on the pile, is also proposed for the estimation of its capacity.