Visualization of the Fragmentation of a Weak Granular Material under Uniaxial Confined Compression

Abstract

This study reports the crushing of a weak granular material during compression. Roasted chick peas were used to model granular materials. The chick peas were chosen because of their size, availability and easiness of crushing under compression. A series of uniaxial confined compression tests were run on the chick peas to visualize their mode of fragmentation. The chick peas were subjected to uniaxial compression stress tests that varied between 0 and 1527.9 kPa. The results from these tests were used to create: (a) an e-log σ curve; (b) to determine how many chick peas were broken and how many remain intact after compression; (c) to run sieve analysis to determine how the gradation of the samples changed as the applied vertical stress increased in value; and (d) to determine how the crushing occurred in the samples. To visualize the evolution of crushing in the samples, a transparent cylinder was used in the testing program. The evolution of crushing of the samples in the laboratory were compared that obtained from a numerical simulation of the compression tests. The numerical simulation used the Discrete Element Method. The location where the crushing took place in the laboratory and in the simulation compared well. A fractal analysis was also performed on the laboratory samples. Fragmentation fractal dimensions were determined. The fractal analysis indicated that the fragmentation fractal dimension increased with the level of crushing of the particles in the samples. Thus, the fragmentation fractal dimension can be used as a measure of the level of particle crushing.