Vertical bearing capacity of bucket foundations in sand

Abstract

Bucket foundations are widely used to support offshore structures. The vertical capacity of bucket foundations in clays has been extensively studied. However, the unique load transfer characteristics of bucket foundations in sands are not well documented. We perform a series of two-dimensional axisymmetric finite element analyses using the Mohr-Coulomb model following a non-associated flow rule. Because the depth-to-diameter ratio of a bucket foundation is much lower compared with that of a pile, a higher level of arching is shown to occur in the soil. A pronounced increase in the horizontal stress and a corresponding increase in the shaft resistance (Qs) are observed. The arching also causes the failure surface to widen due to additional vertical stress imposed on the soil. Based on numerical results, predictive equations for Qs and a combined shape and depth factor for the base capacity (Qb) are proposed for bucket foundations in sands that follow a non-associated flow rule.