An experimental study on the influence of the coordination number on grain crushing

Abstract

In soil mechanics, the material behaviour is significantly affected by grain crushing. This energy dissipating mechanism, along with the frictional rearrangement of grains, is responsible for the energy loss associated with plasticity. However, the micromechanical factors at the grain scale have not been studied by constitutive models which tend to focus on macroscopic parameters. In this study, the influence of the coordination number on the fragmentation of a single cylindrical grain specimen has been examined with a new device by which a series of multipoint crushing tests has been conducted. Experiments conducted with this device have shown the importance of the contacts number, position, type and force in the fragmentation of the individual grain. The results, analysed by imaging techniques, demonstrate that the existing models treating grain rupture are indeed incapable of reproducing the observed fragmentation. Two types of cracks were distinguished, each corresponding to a different crack mode, depending on the contact arrangement. The results of this study could be integrated into fragmentation models for predicting the occurrence of cracks, and the shape of the resulting fragments.

Keywords:

• grain crushing test
• coordination number
• fracture mode