A plasticity‑based upper‑bound prediction model incorporating shank effects for drag embedment anchor behavior in layered clay seabed

Abstract

The installation of drag embedment anchors (DEAs) in layered seabeds presents significant challenges for predicting embedment trajectory and bearing capacity. This paper develops an analytical upper‑bound plasticity model that explicitly incorporates yield mechanisms of both fluke and shank, as well as transition zones between adjacent soil layers. The prediction model of anchor motion, rotation, and capacity are validated against full‑scale field tests in the Gulf of Mexico and Liuhua platform, as well as laboratory and numerical data for layered profiles in the South China Sea and Bass Strait. A comprehensive parametric study is conducted to assess the influence of stiff‑layer strength ratio, layer thickness, and fluke–shank angle on the ultimate embedment depth and load capacity. Key findings include: (1) a critical strength ratio ($s_{u,ratio}$≈7.45) beyond which penetration fails; (2) while layer thickness does not control penetrability, it linearly increases ultimate embedment depth when the stiff layer is penetrable and moderately thick; and (3) an optimal fluke-shank angle exists that balances tip stress concentration for penetration with adequate bearing area for capacity. These findings provide practical design guidance for the effective deployment of DEAs in stratified seabed.