Clay below the micron

Abstract:

The mechanical response of geomaterials is intricately linked to the interactions between particles. Understanding particle-scale interactions is crucial for advancing fundamental knowledge in soil mechanics and developing physics- based models corroborating existing continuum-based approaches. Exploring the microstructural origins of emerging responses at the continuum scale in soils often centers around coarse grained soils. Laboratoy X-ray micro-computed tomography and particle-scale models are nowadays widely used in research on the behaviour of sand.

In contrast, research in micromechanics of clayey soils has been slow to progress due to the challenges associated with studying the evolution of fabric at the submicron scale using conventional techniques such as Scanning Electron Microscopy (SEM) and Mercury Intrusion Porosimetry (MIP). While these methods provide valuable insights into the microstructure of clay, they are limited by the necessary sample preparation processes, such as pore fluid replacement and surface treatment, that alter the natural configuration of the fabric.

These limitations can be effectively overcome with non-invasive X-ray techniques, facilitated by recent advancements in 4th generation synchrotron sources that enable achieving the essential submicron spatial resolution for studying fine-grained soils. This study employs an unparalleled combination of high-resolution nano X-ray Computed Tomography (XCTs) and Small-angle X-ray Scattering (SAXS) to experimentally quantify the three-dimensional (3D) fabric of saturated kaolin clay samples that are consolidated in 1D compression.

Using the synchrotron-based imaging instrument available at the beamline ID16B of ESRF, it was possible to fully resolve the 3D network between kaolin particles, capturing, for the very first time, 3D images of individual clay platelets in their natural (undisturbed) state. Using the SAXS/WAXS instrument available at the CoSAXS beamline of MAXIV synchrotron, it was also possible to monitor the evolution of clay fabric over time. The measurements presented in this study are acquired from 1D-consolidated Speswhite Kaolin clay samples (diameter of 300 μm) saturated with different pore fluids to induce diverse material fabric.

Short bio:

Dr. Angela Casarella is a postdoctoral researcher at Chalmers University of Technology in Gothenburg, Sweden. She holds a PhD in geomechanics from Université Grenoble Alpes, where her research focused on the multi-scale investigation of the thermomechanical behavior of non-active clay. Her current work continues exploring the micromechanics of clays, leveraging advanced techniques such as synchrotron x-ray imaging and scattering. With a strong interdisciplinary approach, Angela aims to bridge fundamental research and practical applications in geotechnical engineering, particularly in the development of engineered geomaterials for both civil and non-civil engineering applications.