Characterisation of calcareous sediments from the U.S. Southern Atlantic Outer Continental Shelf

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4. Characterisation of calcareous sediments from the U.S. Southern Atlantic Outer Continental Shelf

Calcareous sediments of biogenic origin are prevalent throughout the worlds low latitude seabed, including the U.S. Southern Atlantic Outer Continental Shelf (OCS) and in the vicinity of offshore wind call areas recently leased through the United States Bureau of Ocean Energy Management. These sediments comprise the skeletal remains of calcium carbonate bearing marine micro- and macro-organisms and their bioclasts, and the grains can vary from hollow round thin-walled foraminifers to bioclasts with highly angular features. Geotechnical design in calcareous sediments is challenging owing to the many uncertainties related to their microscale properties and have been problematic for offshore infrastructure due to the high compressibility and low cyclic strength. To date, no offshore wind developments have been installed in offshore calcareous sediments and it is not yet certain how they will impact the designs of foundations for offshore wind. This study uses non-invasive X-ray micro-computed tomography (µCT) and advanced three-dimensional (3D) image analysis techniques to visually classify and quantify the morphology of calcareous sediments collected during U.S. Government surveys with grab samples off the United States Southern Atlantic coast. The statistics of particle shape parameters and basic index properties of calcareous sediments off the Southern Atlantic OCS are compared to that of previously studied calcareous sediments from Western Australia. The findings presented add to a very limited geotechnical data set of calcareous sediment from the Southern Atlantic OCS and should be helpful for future offshore wind developments in these regions.

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

2 - Site characterization, in-situ and laboratory testing, measurement