Towards a simple design procedure for dynamically embedded plate anchors

Abstract

Dynamically embedded plate anchors (DEPLAs) are a promising option for anchoring floating facilities in deep water, as relative to current technology such as suction caissons, the anchor will be much smaller and less expensive to install. This paper considers data from the final stage of an experimental campaign that has been undertaken as a preliminary step towards qualification of the DEPLA at full scale. The experiments involved field testing of a 1:4·5 reduced-scale DEPLA in approximately 50 m water depth at a site off the west coast of Scotland. Measurements in the tests included accelerations during free fall in water and embedment in soil, and pullout resistance as the DEPLA was loaded to failure and subsequently retrieved to the deck of the installation vessel. The acceleration data are used in the paper to explore the suitability of strain rate formulations for scaling the undrained shear strength to values appropriate for dynamic penetration, and to demonstrate the potential for a dynamic penetration model to predict the final anchor embedment depth. The paper finishes by summarising output from the embedment model in a simple design chart that can be used to scale a DEPLA for a given mooring line load.