A theoretical model for analyzing the behavior of drag anchors in layered soils

Abstract

Drag embedment plate anchors (drag anchors) play an important role in deepwater mooring systems of various offshore applications, attributed mainly to their large capacity/weight ratio. However, there are still challenges in accurately determining the trajectory and the final embedment position of the anchor in the seabed under the installation drag force, especially when the seabed encounters complexities such as layered soils with both cohesive and cohesionless layers. The present work aims to develop a theoretical model for drag anchors that is capable of analyzing the anchor behavior in layered soils, based on rational mechanical and analytical models. The layered soils are composed of different cohesive and cohesionless layers with various soil strengths. The effect of anchor lines in layered soils is coupled in analyzing the anchor behavior. By fully describing the complicated soil resistance to the anchor at the interface of adjacent layers and in layered soils, the theoretical model is able to analyze the anchor behavior in three-layered soils with two interfaces, covering general cases of layered soils for drag anchor installation. Comparative studies confirm the efficiency and veracity of the developed theoretical model. Being an application, various cases are designed and analyzed by the theoretical model to explore the complexity and variety of the anchor behavior in layered soils.