Image-based modelling of shelly carbonate sand for foundation design of offshore structures

For the most part, carbonate soils are of biogenic origin comprising skeleton bodies and shells of small organisms, the shelly carbonate sands. Owing to the complex microstructure of these soils, there are many uncertainties related to their mechanical behavior, in particular, regarding their high compressibility. Aside from obvious safety concerns, the inability to predict the behavior of carbonate sands involves extensive remedial measures and leads invariably to severe time delays and increased construction costs. This study makes use of 3D images of the internal structure of a shelly carbonate sand under compression on a small oedometer placed inside an x-ray scanner. The images are first used to gain insights into the grain-scale properties of the material and then the soil microstructure is virtualized and simulated within a framework of combined discrete–finite-element method. This study contributes towards a better understand the grain-scale phenomena shaping the macro response of shelly carbonate sands, which differs considerably from more commonly studied silica sands of terrigeneous origin.