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Abstract With the increasing utilization of suction anchors in mooring systems, field surveys have observed seabed trenches near suction anchors caused by anchor chain motion and soil erosion. The presence of these trenches significantly reduces the pull-out capacity of suction anchors, emphasizing the need for attention. This study investigates the impact of seabed trenches on the undrained pull-out capacity of suction anchors at an optimal padeye depth through a series of finite element analyses. Rectangular cross section trenches are considered in this study. The effects of trench size, trench distance, trench shape and local scour on reducing the pull-out capacity of suction anchors are systematically examined. Furthermore, we present an optimal design approach for suction anchors considering seabed trenches that addressed two aspects: (a) determining whether higher pull-out capacity can be achieved by relocating the anchor padeye to a shallower depth and reducing trench depth; and (b) identifying the optimal anchor aspect ratio considering material cost and seabed trench conditions. These analyses provide valuable insights for practical design considerations when dealing with trench-related issues encountered by suction anchors.
Zhang et al. (Sun,) studied this question.