The dynamically embedded plate anchor (DEPLA) is a rocket-shaped anchor that penetrates to a target depth in the seabed by using kinetic energy obtained through free fall and by the anchor's self-weight. After embedment, the central shaft is retrieved leaving the anchor flukes vertically embedded in the seabed. The flukes constitute the load bearing element as a plate anchor. This paper presents initial field data from a series of tests using a 1:20 reduced scale anchor in a lake underlain by very soft clay. Results indicate that the DEPLA exhibits similar behaviour to other dynamically installed anchors during installation, but with much higher capacities, up to 27 times the dry weight of the anchor.

1. Introduction

Depletion of oil and gas deposits in shallow waters (<500m) has required the exploration and development of reserves in ultra-deep waters (1500–3000m) (Colliat, 2002). Floating structures are utilised in deep water, as it is not feasible to use fixed drilling and production platforms. Deepwater installations are typically moored using vertical, taut leg or semitaut leg mooring systems. These systems are designed to have high angles of inclination with the mudline (up to 90° in the case of vertical mooring systems). Installation costs of conventional anchoring systems are highly dependent on water depth (Richardson et al., 2005). Thus deepwater mooring systems require anchors that can sustain significant components of vertical load, while maintaining installation costs at a reasonable level (Ehlers et al., 2004). O'Loughlin et al. (2012) describe a new anchoring system referred to as the dynamically embedded plate anchor (DEPLA). This is a hybrid anchor system that combines the advantages of vertically load anchors (that sustain significant vertical load) and dynamically installed anchors (requiring no external energy source or mechanical operation during installation).

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