Acoustic emission monitoring of crushing of an analogue granular material

A two-dimensional (2D) analogue material formed of rod cylinders of chalk is tested under one-dimensional (1D) oedometric loading conditions. Passive non-destructive acoustic emission (AE) monitoring technique is used to document the occurrence of crushing of individual particles. While the AE activity is recorded by a sensor placed on the sample boundaries, the AE signals are also corroborated with the observations based on video records of the exposed face of the 2D sample, as well as vertical loading and displacement measurements of the global sample. In the process, 1D tests on individual cylindrical rods were also conducted and their AE crushing signatures compared with the AE data recorded at the 2D sample scale. While AE signal features can capture the particle crushing in the 2D granular systems, their occurrence shows high complexities driven by internal crushing particle mechanisms and geometrical position of particles with respect to the AE monitoring device. The frequency content of AE signals shows some evidence of the existence of an AE signature for a typical particle crushing mechanism, which may be a consequence of the dynamic properties of the whole system.