Non-uniqueness of critical solid fraction considering boundary conditions and strain-rate effects--颗粒学报PARTICUOLOGY

Xu, M., Zhang, Z., Huang, X., & Hanley, K. J. (2021). Non-uniqueness of critical solid fraction considering boundary conditions and strain-rate effects. Particuology, 54, 37-49. https://doi.org/10.1016/j.partic.2020.04.001

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

Mingze Xu ^{a b}, Zixin Zhang ^{a b}, Xin Huang ^{a b *}, Kevin J. Hanley ^c

a Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
b State Key Laboratory of Geotechnical Engineering, Ministry of Education, Tongji University, Shanghai 200092, China
c School of Engineering, Institute for Infrastructure and Environment, The University of Edinburgh, Edinburgh EH9 3JL, United Kingdom

10.1016/j.partic.2020.04.001

Volume 54, February 2021, Pages 37-49

Received 7 October 2019, Revised 28 March 2020, Accepted 14 April 2020, Available online 25 May 2020, Version of Record 28 January 2021.

E-mail: xhuang@tongji.edu.cn

Highlights

• Critical solid fraction is lower in rigid-wall condition than in periodic condition.

• Critical solid fraction decreases with increasing loading rate.

• Particles cluster closely to the rigid-wall boundaries at high loading rates.

• Force transmission network is pseudo-stable at high loading rates.

Abstract

The critical solid fraction (ϕ_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 ϕ_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 ϕ_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.

Graphical abstract

Keywords

Jamming transition; Jamming density; Strain rate dependency; Boundary effects

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