Finite-Element Analysis of the Lateral Load Response of Monopiles in Layered Sand

Abstract

Most of the existing design methods for laterally loaded monopiles were developed for uniform soil profiles. The application of such design methods in cases involving layered sand profiles can lead to incorrect capacity estimations. In order to investigate the impact of the soil layering on the response of monopiles to lateral loads and to develop a design method that is applicable to layered soil profiles, a series of three-dimensional (3D) finite-element (FE) analyses were performed on laterally loaded monopiles embedded in layered sand profiles using an advanced two-surface-plasticity constitutive model. The analyses take into consideration a wide range of pile geometries (pile diameter, slenderness ratio, and wall thickness), load eccentricities, sand types and relative densities, and layered soil profiles. The study examines the change of the lateral capacity of a monopile in a two-layer sand profile as the top layer thickness varies, as well as the impact of the presence of a thin loose-sand layer in a dense-sand profile on the pile lateral capacity. Based on the results of these analyses, a set of design equations is proposed to estimate the lateral capacity and load-rotation response of monopiles in layered sand profiles. The proposed method accounts for the 3D pile–soil interaction and provides estimates of the lateral capacity that are in close agreement with those obtained from the 3D FE analyses.