Pull-out capacity of an inclined embedded torpedo anchor subjected to combined vertical and horizontal loading

Abstract

Abstract Whilst the installed torpedo anchors in offshore practice are often characterized with off-verticality, the effect of inclination on the anchor pull-out capacity has seemingly received little attention in the research literature. This paper presents a numerical study on the pullout capacities and failure envelopes of inclined embedded torpedo anchors subjected to combined vertical and horizontal loading. Using Coupled Eulerian–Lagrangian finite element method, effects of load inclination, azimuthal angle of pull-out plane and anchor inclination were sequentially evaluated. It was found the most critical pull-out plane is the one that coincides with anchor plane towards the anchor inclination direction. Its corresponding failure envelope, which can be well fitted by a closed form expression, gives the conservative estimation of anchor pull-out capacities. The comprehensive parametric investigation indicated this conservative failure envelope is mainly affected by anchor inclination and soil’s strength gradient. A series of tables with fitting constant values appropriate for different strength and inclination conditions were furnished. On these bases, a simple design procedure was developed for estimating the ultimate pull-out capacities of inclined embedded torpedo anchors. The outcomes of this work are likely of help for engineers to factor the anchor inclination into the design practice of torpedo anchors.