Scour development around spudcan foundations of varying geometries

This study experimentally investigated the influence of spudcan geometry on local scour development through steady-current tests on models with conical angles (α) ranging from 60° to 180° and diameters (D) between 50 and 150 mm, under both loaded and unloaded conditions. Additional factors included model material (aluminium versus acrylic), tip geometry, and the time-dependent evolution of bearing area during scour. The results provide new insights into scour development around spudcans, which represent low–aspect–ratio footings on the seabed. Applied vertical load was found to substantially accelerate scour, with strong horseshoe vortices forming at the spudcan shoulder and producing more than twice the scour depth observed in unloaded cases. Model material and tip geometry exerted negligible influence, validating the use of transparent acrylic models without tips for visualisation studies. For α = 60° and 150°, equilibrium upstream scour depth (S_c) was reached within approximately 6 h on the experimental scales, irrespective of conical angle. Increasing the diameter raised the absolute scour depth, while the normalised depth (S_c/D) remained nearly constant, demonstrating geometric similarity. Sharper spudcans (lower α) generated significantly deeper scour, with S_c nearly doubling from blunt to sharp configurations, whereas the flat-base (α = 180°) produced minimal scour due to distributed flow resistance. Downstream scour (S_f/D) showed no systematic dependence on α, reflecting the identical top-shoulder geometry governing wake vortices. The bearing area ratio (ζ) exhibited a two-phase trend: an initial rapid reduction to around 0.20, followed by recovery toward unity as scour cavities stabilised and the spudcan made approximately full contact with the seabed. Sharper spudcans displayed faster loss and earlier recovery, while diameter exerted no significant influence on the evolution of ζ.