Microscopic dynamics of sand particles based on X-ray computed tomography and in-situ triaxial compression

X-ray computed tomography (CT) and in-situ triaxial shear test were combined to analyze the microscopic dynamics evolution of Ottawa sand under triaxial compression. A total of 15 X-ray scans were taken during the experiment. The particles were separated by the image segmentation algorithm and reconstructed by spherical harmonic functions. The particles were matched exactly and tracked during the loading process based on the multiscale morphological indicators of particles, and the evolution of microscopic dynamics and microscopic structural indicators, such as particle displacement, rotation, local non-affine motion, and local porosity were analyzed. During the shear process, the vertical displacement distribution of the particle system presents two conical regions, and the rotational distribution of the particles exhibits obvious X-shaped shear bands. The local non-affine motion, which was used to measure the local plastic deformation, was significantly correlated with the local volume fraction, suggesting a causal relationship between the microscopic dynamics and particle microstructure, i.e., plastic deformation was more likely to occur where the local free volume was large. © 2023 Zhejiang University. All rights reserved.