Evolution of Percolating Force Chains in Compressed Granular Media

The evolution of effective force chains percolating through a compressed granular system is investigated. We compressed an ensemble of spherical particles monitoring the macroscopic constitutive behavior and the acoustic signals emitted by microscopic rearrangements of particles. We applied the continuous damage model of fiber bundles to describe the evolution of the array of force chains. The model provides a nonlinear constitutive behavior in good quantitative agreement with the experimental results. The amplitude distribution of acoustic signals was found experimentally to follow a power law of an exponent $\delta =1.15\pm 0.05$, which is in good agreement with the analytic solution of the model.

Figure 1

Experimental setup and sketch of the array of force chains used in the model.

Figure 2

Experimental constitutive behavior for small strain values and comparison to the theoretical results.

Figure 3

Acoustic signal amplitude. A power law of an exponent $\delta =1.15$ was fitted to the size distribution.

Figure 4

Event sizes $s$ occurring during the loading history $\epsilon$ and their size distribution $D(s)$ on a log-log plot.