Numerical Study on Keying Capacity of Gravity Installed Anchors in Sand

Abstract

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.