Geomechanics at the particle scale: the potential of image-based approaches

Dr Joana Fonseca

Soils are granular systems composed of particles with diverse shape, size and mineralogy. Soil properties, such as strength, permeability and compressibility are determined by the interaction of soil particles and associated evolving microstructures. Conventional laboratory testing of soils, largely based on measurements at the sample boundaries, entails an implicit analogy between the particulate and continuum material. In this talk, a case is made for why from an engineering perspective it is worth looking at soil behaviour at the particle scale. The focus is on the use of image-based techniques, particularly x-ray tomography, to shed light on less understood aspects of soil behaviour resulting from the granular complexities of soils. Firstly, results from recent studies are presented, which include: The role of particle-to-particle contact topologies in explaining the differences in strength and stiffness measured for intact and reconstituted samples of the same sand. The damage mechanics underlying the failure of sandstones with different degrees of cementation.  The particle-scale phenomena leading to partial drainage behaviour of silts under CPTU. The high angularity and intra-granular voids leading to unlocking mechanisms and the collapsible microstructure underpinning high deformations in shelly carbonate sands. Finally, the use of image-based insights to improve modelling of soils is discussed.

Dr Joana Fonseca Senior Lecturer In Geotechnical Engineering City University of London

Joana Fonseca is a Senior Lecturer in Geotechnical Engineering at City, University of London and a Chartered Civil Engineer (Portugal). She received her PhD in Geotechnics from Imperial College London in 2011 and did post-doctoral research at the Laboratoire 3SR in Grenoble and at the Department of Materials at Imperial College. Her research focuses on particulate soil mechanics and is underpinned by her 5-year experience in engineering consultancy. Joana uses image-based techniques to link particle scale interactions to bulk behaviour of soils. She is a past-editor for the Canadian Geotechnical Journal and Géotechnique. She is the Guest Editor for the Special Issue “Recent Advances in Image-Based Geotechnics” for the Journal of Imaging and the recipient of The University of Melbourne 2024 International Visiting Fellowship award.

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