Limiting aspect ratio for suction caisson installation in clay

Suction caissons have emerged as an increasingly popular option for anchoring systems. To date, suction caissons have been limited to relatively low aspect ratios. However, as new offshore fields are developed in deeper water, higher aspect ratio caissons are needed in order to provide higher capacity, particularly in situations where a large upward component of load has to be withstood. Theory suggests that a limiting aspect ratio exists beyond which complete caisson installation cannot be achieved due to upheaval of the internal soil plug. This paper presents the data from a series of laboratory tests, aimed at establishing relationships between caisson penetration, installation pressures and volume of evacuated fluid and comparing results with the theoretical behaviour. Model caissons of various aspect ratios were installed in both normally consolidated and overconsolidated kaolin clay. The data exhibited excellent consistency but indicated limiting aspect ratios before plug failure that were somewhat lower than simple theory suggests.