Multiscale modelling of shelly carbonate sands for foundation design of offshore structures (MuMShell)

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Carbonate soils cover over 40% of the world's seabed, where offshore structures, pipelines, artificial islands and other marine structures are founded. For the most part, carbonate soils are of biogenic origin comprising skeleton bodies and shells of small organisms, the shelly carbonate sands. These soils are a complex and poorly understood material as evidenced by a number of accidents reported during platform installation in the 80s. As a consequence, shelly sands have been placed into a niche classification of "problematic soils" in most design guides. While failures are now relatively rare, conservative methods and high factors of safety are commonly used. Understanding the behaviour of shelly carbonate sand is critical for the design of foundations for offshore structures. In particular, understanding the physical phenomena taking place at the microscale has the potential to spur the development of robust computational methods to be integrated into novel or existing design approaches.Image-based geomechanics is a fascinating research field that has the potential to transform the way soils are investigated and modeled. The ability to follow deformation at the microscale has helped to answer fundamental questions about the soil behaviour observed at the macro-scale. The proposed research uses 4D synchrotron x-ray imaging and post analysis to investigate the kinematics and the strain maps of a shelly carbonate sand under compression. The outcomes will contribute scientific understanding on the multiscale behaviour of shelly carbonate sands. This will form the basis to develop fabric-informed constitutive models to better predict the soil response, thus improving design practices for foundations of offshore structures. The ambition of this project is to contribute towards safer, less conservative and more sustainable ground structures and reduce the financial risks associated with unforeseen ground response during construction of offshore foundations. This multiscale methodology and image algorithms here developed, will be valuable to the broad granular media community to simulate mechanical processes in additive manufacturing, mining, food and pharmaceutical industries.