Assessment of the Group Behavior of Torpedo Anchors Through Finite Element Modelling

In Brazilian offshore fields, torpedo anchors are extensively used in deep-water mooring systems. These anchors are known to be cost-effective and capable of withstanding high vertical loads. Despite their successful usage in the offshore industry, the increasing loads imposed by the mooring systems in ultra-deepwater applications demand higher anchor holding capacities. In this scenario, a possible solution is to consider a group of torpedo anchors, which has not been investigated. Hence, this article uses a three-dimensional nonlinear finite element model to present a numerical study on the group behavior of typical torpedo anchors embedded in a purely cohesive isotropic soil. In this model, the soil is simulated with solid elements representing its nonlinear behavior and the large deformations involved. The torpedo anchors are also modeled in detail with solid elements. Moreover, the anchor-soil interaction is addressed with contact finite elements that allow relative sliding with friction between the surfaces in contact. Several analyses are conducted to understand the response of this type of anchor when installed in groups. The research addresses some essential features in group analysis, such as anchor spacing, connection between the anchors, and soil-structure interaction. Additionally, the results are compared with those from a single anchor installed in the same conditions to highlight the torpedo anchor group efficiency.