Experimental investigation of suction-assisted penetration of compartmented bucket foundations

Compartmented bucket foundations (CBFs) represent a promising alternative to conventional offshore wind turbine foundations, offering enhanced structural stability and bearing capacity. However, the compartmented internal configuration of CBFs complicates the soil-water-structure interaction and poses unique challenges for suction-assisted installation, particularly in sandy soils where seepage effects are prominent. This study presents a series of model tests investigating the suction penetration behavior of both mono bucket foundations (MBFs) and CBFs in homogeneous sand. By varying bucket wall thickness, bulkhead thickness, and mid-chamber size, the influence of compartment geometry on penetration suction was evaluated. Results show that suction installation significantly reduces penetration resistance compared to jacking, which requires up to 8.7 times resistance for MBFs and 15.8 times for CBFs compared to suction-assisted penetration. Additionally, while increased wall and bulkhead thickness lead to higher suction demands, variations in mid-chamber size have minimal impact. Moreover, a theoretical model originally developed for MBFs was extended to incorporate additional bulkhead-induced resistance. The modified model provides accurate predictions for suction pressure, particularly during the stable penetration phase. This work advances the understanding of CBF installation mechanics and offers practical guidance for optimizing suction bucket designs in offshore wind applications.