Abstract
This study explores the development of an innovative anchoring foundation element, the "Retrievable Ocean Petal Anchor (ROPA)," appropriate for mooring floating Marine Renewable Energy (MRE) devices. This innovative ground anchor system can be used in various seabed conditions, not only providing flexibility in terms of its installation but also allowing for easy retrieval. The proposed anchor configuration is such that the anchor has several flanks/petals that are folded during installation, which is aided by built-in water jetting mechanisms, and then radially expanded once installed into the subsurface profile. This radial expansion is facilitated by continuing to fluidize the soil through the introduction of a high-pressure seawater jet, through a truncated cone installed at the ROPA tip, to fluidize the seabed as the petals of the anchor flare out during deployment. The flanks expand and fold with a sliding connector ring over a central bar. The sliding components are protected against sand intrusion through the use of housing enclosures for sustained long-term performance. Once the high-pressure jet stream ends, the seabed returns to its natural state, providing resistance to loading induced from the marine energy device. The retrieval process is envisioned to be the inverse of the installation process. ROPA can be installed with minimal noise effect, and it is designed to handle multiaxial loading, making it suitable for a variety of applications.
The work herein examines the influence of various ROPA geometries on the lateral and axial capacities of ROPA in sandy seabeds. Numerical modeling within the PLAXIS 3D framework is employed to investigate the influence of the number, deployment angle, and embedment depth of the ROPA petals, in conjunction with soil properties, on the lateral and axial capacity. The 3-D numerical model is employed for upscaling a prototype ROPA, facilitating the modeling of larger ROPA dimensions to field-scale equivalents. Analyses are conducted to evaluate the potential lateral and pullout capacities achievable when induced by mooring lines anchoring wave and current converters. With upscaling, the results explore the potential of utilizing ROPA as a permanent anchoring system with performance that meets serviceability and ultimate limit states as specified in IEC standards and DNV code.