Investigation of the Penetration Resistance Coefficients for the CPT-Based Method for Suction Bucket Foundation Installation in Sand

The current practice for estimating the penetration resistance of suction bucket foundations requires breaking down the penetration resistance into tip and skirt resistance components. Cone penetration test (CPT)-based methodology correlates these components to the cone resistance measurements through empirical coefficients. In this study, an experimental campaign involving suction installation, jacking, and pullout tests on suction buckets with a large aspect ratio (i.e., L/D = 1, where L is the skirt length and D is the diameter) atop sand deposits of varying relative densities was performed to identify the important factors that are involved in the installation procedure but are not well understood. The following factors were studied: the influence of the friction area in caissons of round and modular shapes, the dilative behavior of sand, the soil-structure interface friction angle, and the penetration depth. The experimental results of the jacking installation tests indicated that a larger friction area significantly increased the penetration resistance; however, this effect was completely diminished when foundation suction-assisted penetration was used. Based on these results, modified friction resistance and tip resistance factors in the empirical expressions accounting for the relative density and penetration depth were proposed. Finally, the required suction pressure was back-analyzed by utilizing these empirical relations, reduction factors, and the critical pressure.