Effects of multiple parameters on the uplift suction of subsea structures

Abstract

Seabed-resident autonomous underwater vehicles (SRAUVs) deployed for extended periods may become difficult to detach from the seabed owing to negative pore pressures within sediments. In this study, numerical simulations are performed based on the modified Cam-Clay model to investigate the mechanisms and key factors governing soil suction forces during detachment. The effects of loading conditions (preload magnitude and consolidation duration), lifting conditions (lifting velocity and eccentric lifting strategy), and physical conditions (structure geometry and sediment type) on the pore pressure and suction development are analyzed. Increasing the preload significantly enhances negative pore pressure during lifting. Longer preload durations amplify suction until full consolidation, after which suction stabilizes. Suction is effectively mitigated by reducing the lifting velocity to approximate fully drained conditions or by applying eccentric lifting strategies. Compared with plates, cylindrical structures generate higher negative pore pressures owing to stress concentration effects. Clayey sediments, owing to their low permeability, produce greater suction forces than sandy sediments. Overall, this work identifies optimized structural designs and detachment strategies (e.g., eccentric lifting and staged loading) to reduce suction forces, providing engineering guidance for the safe recovery of SRAUVs.