Cyclic Capacity and Diving Potential of Novel Fish Anchor in Calcareous Silt

Abstract

This paper reports the performance of a novel dynamically installed fish anchor under cyclic operational loading in calcareous silt. The investigation was carried out through a series of centrifuge model tests. The results demonstrate that the pullout capacity of the fish dynamically installed anchor (DIA) subjected to cyclic loading is dependent on the combination of cyclic mean load, cyclic load amplitude, and number of cycles. A design contour is proposed for estimating the anchor capacity under various magnitudes of cyclic load. The evolution of anchor displacement, inclination, and excess pore pressure are quantified and their influences on the fish DIA capacity are highlighted. With a tip embedment depth of 1.02–1.43 times the anchor length during dynamic installation, the fish DIA was found to dive in calcareous silt for mooring mudline inclinations ≤ 45° under both monotonic and cyclic operational loadings, whereas by contrast, the OMNI-Max anchor with tip embedment of 1.4–2 times the anchor length did not dive for inclinations as low as 1°–10°. As such, the fish DIA has the potential for efficient anchoring to allow economic development of oil and gas reserves in deep water with calcareous seabed sediments.