Centrifuge modelling and the modified limit equilibrium prediction for drag embedment anchor installation in sand

Abstract

This study presents the measured trajectory, orientation, and capacity of drag embedment anchors (DEAs) in centrifugal installation tests conducted in sand. The 6-degree-of-freedom data obtained from the magnetometer directly verified two kinematic behaviors during the installation of DEAs: (1) the penetration of the drag anchor aligns with the orientation of its fluke; (2) its rotation corresponds to variations in the tension angle of the anchor line at the padeye. The slight increase in shear wave velocity of the soil beneath the fluke, as measured by the bender elements, directly confirmed the presence of the force behind the fluke. Based on these experimental observation, a modified DEA installation prediction model was developed using the limit equilibrium method. The predicted trajectory, pitch, and capacity of the model align well with the experimental results. The model also revealed the mechanism behind the limited capacity of DEA to resist vertical loads: an increase in the loading angle at the padeye decreases the failure angle, which reduces the volume of the three-dimensional failure soil wedge and, consequently, the anchor capacity. Finally, a series of parametric studies were conducted to analyze the influence of sand properties, the initial state of anchor, and other anchor parameters on the kinematic behavior and capacity performance of DEAs.