Suitability of helical anchors for mooring a wave energy converting system

This paper presents a brief description of a new wave energy converter system to be erected at prototype scale off the Belgium coast in 2018. The suitability of helical anchors for mooring such a floating device is analyzed on the basis of 1 g load tests on scale model anchors in saturated sand. Helical anchors with one helix of varying diameters are tested in monotonous pre- and post-cyclic pull-out tests as well as in cyclic multistage tests. The monotonous pre-cyclic pull-out tests predominantly serve as a reference quantity to define the magnitude of cyclic loading in the multistage tests via the so-called cyclic load ratio. The cyclic load tests reveal that a stabilization of the accumulated anchor displacements can be reached for small cyclic load ratios especially for pre-stressed anchors. However, the displacement accumulation significantly affects the anchor post-cyclic bearing capacity which needs to be sufficiently considered in the design.