An X-ray computed tomography (CT) assessment of soil movement during suction caisson installation

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4. An X-ray computed tomography (CT) assessment of soil movement during suction caisson installation

Suction caissons have been widely adopted for anchoring offshore structures, providing silent installation and the potential for removal and reuse. The pressure difference generated during suction installation can induce significant seepage flow in sands, altering the effective stresses. In some cases, this can cause soil instability and internal erosion or piping and result in installation refusal. This study looks at the development of a method for investigating suction caisson installation in sands using a scale model and non-destructive, non-invasive X-ray computed tomography (CT). Fine sand mixed with coarse-grain markers was used to prepare a model seabed. A precision syringe pump withdrew water at a constant flow rate from a suction caisson model, while water pressure inside the caisson was continuously monitored. To investigate soil deformations during the suction installation process, X-ray CT scans were collected before, between and after two successive suction installation runs. Preliminary experimental data to assess soil deformations and movements near the caisson are presented. Significant internal movement of the soil plug is evident and deformations outside the skirt and below the caisson can be seen from digital image correlation. A simplified seepage analysis provides a means to assess the hydraulic gradient around and inside the caisson during the experiment. It is believed that with further refinement, this may be a viable method to investigate soil deformation and suffusion processes experienced during suction installation refusal. Further work is required to improve the quantitative soil deformation analysis and sample preparation.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

11 - Suction installed foundations and anchors