I-Corps: Multiline Ring Anchor for Floating Offshore Structures

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project is to provide a cost-effective anchor for mooring arrays of floating structures to the seabed, with applications in offshore wind and wave power generation, large scale aquaculture, and coastal protection. Anchorage/mooring system costs can comprise a significant portion of the total capital cost for these types of projects, so cost savings derived from this anchor may improve the economic competitiveness of the overall project. The Multiline Ring Anchor (MRA) has a circular symmetry to permit multiple mooring line attachments to a single anchor, greatly reducing the number of anchors within an array of floating units. The MRA is designed for high efficiency - high load capacity relative to its size - thereby requiring decreased amounts of steel, smaller and fewer transport vessels, and smaller installation and handling equipment. The MRA is also designed to provide resistance to both horizontal and vertical mooring line loads, the latter being essential for taut mooring systems in deep-water developments. Seabed soil conditions are highly variable in U.S. waters, leading to a need for a versatile anchor that can be installed and function in a wide range of soil types. This I-Corps project is based on the merging of two research areas associated with the development of the Multiline Ring Anchor (MRA). The first involves wind and wave modeling to quantify the stochastic, time-varying loads placed on platforms that are transmitted through the mooring lines down to the anchor. This study considers different platform types and both catenary and taut mooring systems. The second research area involves investigation of the geotechnical performance of the anchor when subjected to such loading. This research thrust comprises parallel numerical simulations and geotechnical centrifuge tests of the MRA embedded in clay and sand soils. The geotechnical studies aim to quantify the maximum mooring line loads that the MRA is capable of resisting and to confirm that repeated load cycles will not induce gradual upward ratcheting movements of the anchor, which could deleteriously affect anchor performance. The wind/wave modeling and geotechnical studies will provide insights and knowledge extending beyond the direct focus of this study and can be applicable to other mooring systems and anchors. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.