Experimental study on early scour resistance of solidified sludge for protection of tripod suction bucket foundations

Abstract

Using dredged marine sludge as a scour-protection material offers a route to reuse waste while protecting offshore foundations, but its early-age resistance under hydrodynamic loading remains insufficiently quantified. This study evaluates a novel five-component binder system (cement, fly ash, slag powder, silica fume, and PAM) for tripod suction bucket foundations. Incipient-velocity tests and flume tests were conducted to examine stabilizer proportion (5%–20%), water-to-material ratio (60%–70%), and early curing time (2–64 h). Incipient shear stress reached 8.24 Pa at 16 h for 20% stabilizer proportion and a 65% water-to-material ratio. Performance generally increased with stabilizer proportion and curing time, whereas the water-to-material ratio showed a non-monotonic response with the best performance near 65%. Flume tests showed a progressive failure sequence from surface erosion to boundary block detachment and localized scour behind the rear buckets; a 2.5D protection radius reduced maximum scour depth by 87.1%. A preliminary multiple-linear-regression model was incorporated into an LRFD-based scour framework to link material resistance with scour development within the tested parameter range. These results provide early-age design information for solidified dredged sludge used as scour protection.