Non-uniqueness of critical solid fraction considering boundary conditions and strain-rate effects

Mingze Xu, Zixin Zhang, Xin Huang, Kevin J. Hanley

Research output: Contribution to journalArticlepeer-review


The critical solid fraction (phi_J), which marks the transition between the solid and liquid phases in the jamming diagram, is influenced by several factors. In this study, the dependency of phi_J on strain rate and boundary conditions is examined through discrete element method simulations considering a frictionless polydisperse granular system. Different approaches are used to determine phi_J. The observed boundary effect is due to the nonuniform solid fraction distribution induced by the clustering of particles close to rigid-wall boundaries at high compression rates. The solid fraction distribution within the sample in the rigid-wall simulations approaches that in the periodic-boundary simulations as the compression rate decreases. With increasing compression rate, the major force transmission network contains fewer mechanically stable particles and a less stable force transmission network. This causes jamming of the granular assembly at a lower solid fraction. These force transmission networks, however, are fragile and disintegrate quickly upon relaxation.
Original languageEnglish
Early online date25 May 2020
Publication statusE-pub ahead of print - 25 May 2020


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