The capacity and keying behaviour of strip anchors in dense silica sand is examined in this paper through a series of centrifuge tests conducted at 30g. Tests were conducted adjacent to the Perspex side panel of the centrifuge strongbox to facilitate optical observation and measurements of the keying response. Image analysis shows the failure mechanism to transition from a deep localised rotational mechanism to a shallow block mechanism extending to the soil surface. The onset of this transition coincides with the peak uplift resistance of the plate, which occurs at approximately 65°. The uplift resistance of the plate as it becomes horizontal is in good agreement with a limit equilibrium solution that neglects the normality condition and assumes a failure mechanism that is broadly similar to the eventual failure mechanism of the plate after keying.
Much work has been conducted in recent years on the capacity and keying behaviour of plate anchors in clay, with notable contributions from Gaudin et al. (2006a), Song et al. (2009) and Yang et al. (2012). There have been very few corresponding studies in sand, as clay is the dominant soil type in the deep-water environment in which plate anchors are currently used. However, the installation of floating wave energy converters and wind turbines in water depths of typically less than 100m will require anchoring systems that are suitable for sand deposits. Prior studies on the performance of plate anchors in sand have either considered vertically loaded horizontal anchors (Figure 1a; e.g. Ovesen, 1981; Murray and Geddes, 1987; Dickin, 1994), or horizontally loaded vertical anchors (Figure 1b; e.g. Das et al., 1977, Rowe and Davis, 1982; Merifield and Sloan, 2006). To the authors' knowledge, no studies have addressed vertically loaded vertical anchors (Figure 1c).