Performance of a dynamically installed fish anchor in cohesionless soils

Abstract

This paper assesses the performance of the fish anchor in silty sand deposits with the aim being potentially using the anchor in supporting floating wind turbines in shallow water sandy seabed. A total of seven tests were undertaken in a beam centrifuge. The model fish anchors were dropped from a height of 36.75–57.72 m above ground level. The achieved impact velocities were 17.15–27.42 m/s. The anchor with a dry weight of 1175–1338 kN embedded into the soil deposit to a depth of 0.81–1.18 times the length. The normalized tip embedment depths were plotted in a total energy framework, and explained by a shear resistance method. The embedded anchor was loaded monotonically up to the failure. The peak capacity at failure was found to reduce with increasing the loading (mooring) angle at the mudline to the horizontal. For vertical or 90° loading, the capacity was around 2 times the weight of the anchor submerged in water. The capacity increased to 7.13 times the weight as the loading angle reduced to 0° (horizontal). The strong resistance of sandy soil and higher load inclination at the padeye prevented the diving potential of the anchor.