• The DEA (front)–VLA (rear) configuration with a fluke-back connection achieved the highest embedment depth and ultimate capacity , highlighting the dominant contribution of the rear (VLA) anchor. • A synergistic effect exists between anchor sequence and attachment point, indicating that neither parameter alone can adequately describe system performance. • Larger anchor spacing enhances embedment depth and capacity, though practical design must balance performance and cost. • Increasing plate width or reducing the initial fluke–shank angle decreases embedment efficiency by increasing soil resistance or limiting pitch angle development. • The findings provide new insights into the kinematic mechanisms of tandem anchor systems and offer valuable guidance for the design and optimization of deepwater mooring This study investigates the embedding performance of piggy-backed anchor systems, consisting of a drag embedment anchor and a vertically loaded anchor, through six groups of in-plane model experiments. Particular emphasis is placed on the influence of the anchor sequence—specifically, the positioning of the front and rear anchors. The effects of spacing, attachment point, aspect ratio, and initial fluke-shank angle are also examined. Throughout the experiments, a six-degree-of-freedom magnetometer system was employed to monitor the angle and displacement variations of the anchors within the piggy-backed systems. After evaluating the five parameters, it was determined that the piggy-backed configuration which the front anchor is a drag embedment anchor and the rear one is a vertically loaded anchor with a fluke-back connections—where the rear anchor is attached to the back of the fluke of the front anchor and anchor spacing is 4 fluke lengths—achieved the highest capacity and deepest embedment depth among all tested piggy-backed anchor configurations. Neither increasing the anchor plate width of either anchor nor altering the initial fluke-shank angle resulted in a capacity exceeding that of the prototype. This study elucidates the kinematic behavior of the novel piggy-backed anchor configuration during the embedment process, offering valuable insights for the selection and practical application of piggy-backed anchors.
Wu et al. (Sun,) studied this question.