A pioneering investigation into the particle-scale origin of strength and stiffness of clayey geomaterials

The mechanisms at particle scale that govern the emerging response of (un)saturated fine-grained soils, such as clay and silt, are largely unknown. This is partly attributed to the complexity of the material at this scale (from nanometres to micrometres), where the interactions are no longer solely mechanical (frictional), and partly to the inability to observe experimentally the evolving processes at the appropriate temporal and spatial scales. Furthermore, in unaltered wet samples, the contrast between clay platelets and the fluid in the pore space proves challenging for X-ray tomography based techniques.

As a consequence the current understanding on the role of micro-structure in fine-grained materials is largely inferred from post-mortem analyses on specially prepared samples, e.g. using Scanning Electron Microscopy and/or Mercury Intrusion Porosimetry, in combination with hydro-mechanical or physico-chemical manipulation at continuum scale (> cm). This approach is severely constrained by the adopted ‘static’ observation methods that require destructive sample preparation as well as the poor link between the continuum scale manipulation and the micro-scale response. In addition the destructive nature of this approach makes monitoring of the temporal evolution of the micro-structure impossible.

In the proposed project new experimental avenues for monitoring and material manipulation at the small scale will be explored to enable monitoring the evolving response of fine-grained materials across the scales. In order to have a quick turnaround time to experiment with a wide range of initial conditions and material compositions the focus will be on adopting cost-effective laboratory based manipulation and observation methods that will be benchmarked against reference methods at synchrotron facilities that are less freely accessible.