Experimental studies on suction-assisted installation of the modified suction caisson in dense sand

Abstract

The modified suction caisson (MSC) consists of an internal compartment (IC) and an external structure (ES), being an innovative foundation for offshore structures. Penetration of the MSC into the desired position under the combination of the self-weight and applied suction is an issue for design. Model tests were performed on the MSC in saturated dense fine sand to explore the installation behavior of the MSC. Results show that the optimal method of penetrating the MSC (i.e., the maximum penetration is obtained) is only pumping out the air and water encased in the IC. During suction-assisted installation, subsidence regions around the IC and ES were found. The sand particles in the subsidence regions were found to move downwards along the external walls of the IC and ES. The length of sand particles migration path along the IC is higher than that along the ES, indicating that seepage effect in sand outside the IC is stronger than that outside the ES. Installation mechanisms under various installation methods were elaborated by analyzing the seepage distribution in sand around the MSC. Based on the method proposed by Houlsby and Byrne, modified equations of estimating the required suction of MSC were proposed. The research can provide guidance for the MSC installation design.