Experimental compaction of anisotropic granular media

TL;DR

This study investigates how anisotropic granular media compact over time under vertical stress, revealing that grain shape influences the rate and mechanisms of densification, with detailed experimental insights.

Contribution

It provides experimental data on the compaction dynamics of anisotropic granular media using gamma-ray imaging, highlighting the role of grain shape in relaxation and convection processes.

Findings

Packing fraction evolution is slowed by grain anisotropy.

Relaxation and convection times are of similar magnitude.

Compaction mechanisms depend strongly on grain shape.

Abstract

We report on experiments to measure the temporal and spatial evolution of packing arrangements of anisotropic and weakly confined granular material, using high-resolution $\gamma$-ray adsorption. In these experiments, the particle configurations start from an initially disordered, low-packing-fraction state and under vertical solicitations evolve to a dense state. We find that the packing fraction evolution is slowed by the grain anisotropy but, as for spherically shaped grains, can be well fitted by a stretched exponential. For a given type of grains, the characteristic times of relaxation and of convection are found to be of the same order of magnitude. On the contrary compaction mechanisms in the media strongly depend on the grain anisotropy.