Computed Tomography of Sand Subjected to Heating: Analysis of Particle Displacements

Over the past decades, multiple studies have associated the deformation of coarse-grained soils subjected to temperature variations with complex mechanisms involving particle interactions at the microscale. Despite increasing advances in the understanding of how coarse-grained soils subjected to temperature variations deform at the macroscale, knowledge at the microscale remains limited, with arguably no experimental observations about such particle interactions. This work presents an experimental investigation on particle interactions developing in coarse-grained soils subjected to heating by means of X-ray computed microtomography. Specifically, this work discusses a tomography experiment where particles of F-35 silica sand are subjected to a temperature variation from 30°C to 80°C under zero applied vertical stress in a small container. The displacements of individual particles are analyzed by image analyses on two image scans before and after the heating. The results show that tomography experiments combined with image analyses can provide sufficient accuracy at the microscale to capture particle displacements induced by temperature variations. Heating induces upward particle displacements whose magnitudes increase for particles located at shallower locations in the assembly, suggesting a macroscopic volumetric expansion of sand upon heating that results from the expansion and interactions of individual particles.