Grain size effect on the compression and relaxation of a granular column: solid particles vs dust agglomerates

TL;DR

This study experimentally investigates how grain size and material type influence the compression and relaxation behaviors of granular columns, revealing non-linear force dynamics and relaxation patterns modeled by Maxwell's theory.

Contribution

It provides new insights into the effects of grain size and particle type on granular column mechanics, including force fluctuation behaviors and relaxation modeling.

Findings

Force increases non-linearly with time during compression.

Force fluctuations grow with increasing grain size.

Relaxation follows a Maxwell model with three time scales.

Abstract

We studied experimentally the effect of grain size and maximum load on the compaction and subsequent relaxation of a granular column when it is subjected to vertical uniaxial compression. The experiments were performed using two different types of grains: 1) solid glass beads, and 2) porous beads that consist of agglomerates of glass powder. We found that the compression force increases non-linearly with time, with sudden drops for the case of glass beads and periodic undulations for dust particles. Whereas the grain size effect is small in the average force load, the fluctuations become larger as the grain size increases. On the other hand, the relaxation process is well described by the Maxwell model with three different relaxation time scales.