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

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 pull-out 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.