Eulerian Finite Element Analysis for Uplift Capacity of Circular Plate Anchors in Normally Consolidated Clay

Abstract

Anchors are often used to provide uplift resistance for mooring of boats and floating decks as well as anchoring of pipelines offshore. Anchor is often idealized as a circular plate in the analysis of its uplift resistance. The uplift capacity of circular plate anchor in uniform soil is well documented in the literature. However, the pullout behavior of circular anchor in nonhomogeneous soil is less well studied and forms the motivation of this paper. In order to circumvent computational difficulties associated with severe mesh distortion during the pullout process, the Eulerian large strain, large deformation finite element approach is adopted in this study to investigate the pullout behavior of circular plate in normally consolidated clay. The applicability of the Eulerian numerical model is validated by comparing the numerical results with analytical solutions from lower bound limit analysis for a uniform soil as well as data for a centrifuge test conducted in normally consolidated Kaolin clay. Conventionally, it is generally accepted that the uplift behavior of a plate anchor in a normally consolidated soil can be inferred from that in a uniform soil by adopting the strength at the initial plate position as the reference strength. However, it is observed from the numerical results that the failure mechanisms corresponding to plate anchors in uniform clay and normally consolidated clay are different for the same set of reference undrained shear strength and geometric parameters. This implies that the conventional approach is not always applicable. A direct design method for obtaining the uplift capacity of a circular plate anchor embedded in a linearly increasing soil shear strength profile is then proposed.