Anchors may exhibit various complicated behaviors in the seabed, especially for deepwater anchors including gravity installed anchors (GIAs) and drag embedment plate anchors (drag anchors), stimulating the development of an efficient analytical tool that applies to a variety of anchors. The present paper introduces a unified model for analyzing different anchor behaviors in both clay and sand, consisting of unified concepts, mechanical models, and analytical procedure. The kinematic behaviors of the anchors are classified uniformly as three types, i.e., diving, pulling out, and keying. By utilizing the least-force principle, various anchor properties, such as the ultimate pullout capacity (UPC), failure mode, movement direction, embedment loss, and kinematic trajectory, can all be determined by the combination and analysis of the three behaviors. Applications of the model are demonstrated summarily, by solving the UPC and the failure mode of anchor piles and suction anchors, the kinematic trajectory of drag anchors in a single soil layer or layered soils, the maximum embedment loss (MEL) of suction embedded plate anchors (SEPLAs) and OMNI-Max anchors, and the kinematic behavior of OMNI-Max anchors. Compared to existing theoretical methods, this unified model shows strong applicability and potentiality in solving a variety of behaviors and properties of different anchors under complicated seabed conditions.

Being the latest representative of gravity installed anchors (GIAs), the OMNI-Max anchor can perform comprehensive behaviors in the seabed, like keying and diving, by adjusting orientation and position to derive higher capacity and to avoid anchor failure. During the keying process of GIAs, many factors may influence the keying capacity, such as the embedment depth, the anchor orientation, the rotational center, the bearing area, and the soil strength. Based on the coupled Eulerian–Lagrangian (CEL) technique, large deformation finite element analyses combined with a bounding-surface plasticity constitutive model are performed to investigate systematically the keying behavior of GIAs in sand. A series of analytical cases involving multiple factors are designed and analyzed to explore the effects of various factors on the keying capacity of GIAs, defined by the soil resistance coefficient during keying. The soil resistance coefficient increases with increasing soil density, while it tends to be stable with the increase of the embedment depth. The closer the rotational center approaches to the two ends of the anchor, the greater the soil resistance coefficient becomes. When the loading arm angle is in π/6–π/4, the soil resistance coefficient takes a relatively small value, while the degree of influence decreases with increasing embedment depth. An explicit expression of the soil resistance coefficient during keying is derived to quantify the effects of various factors, whose applicability and accuracy are validated by different ways. These findings are helpful to understand further the comprehensive anchor behaviors and to promote the application of GIAs in offshore engineering.