Effect of aspect ratio on triaxial compression of multi-sphere ellipsoid assemblies simulated using a discrete element method--颗粒学报PARTICUOLOGY

Gong, J., & Liu, J. (2017). Effect of aspect ratio on triaxial compression of multi-sphere ellipsoid assemblies simulated using a discrete element method. Particuology, 32, 49-62. https://doi.org/10.1016/j.partic.2016.07.007

Effect of aspect ratio on triaxial compression of multi-sphere ellipsoid assemblies simulated using a discrete element method

Jian Gong, Jun Liu ^*

State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

10.1016/j.partic.2016.07.007

Volume 32, June 2017, Pages 49-62

Received 26 February 2016, Revised 24 June 2016, Accepted 12 July 2016, Available online 9 January 2017, Version of Record 20 April 2017.

E-mail: junliu@dlut.edu.cn

Highlights

• Stress–dilatancy relationship of ellipsoids could be expressed as a linear equation.

• The aspect ratio influenced the position of critical state lines.

• The particles tended to lie flat at critical state when the aspect ratio was increased.

• The hindrance of rotation with longer particles influenced contact mechanics.

• The anisotropic coefficients with respect to aspect ratio were investigated.

Abstract

Here, we present a numerical investigation of the mechanical behavior of ellipsoids under triaxial compression for a range of aspect ratios. Our simulations use a multi-sphere approach in a three-dimensional discrete element method. All assemblies were prepared at their densest condition, and triaxial compression tests were performed up to extremely large strains, until a critical state was reached. The stress–strain relationship and the void ratio–strain behavior were evaluated. We found that the stress–dilatancy relationship of ellipsoids with different aspect ratios could be expressed as a linear equation. In particular, the aspect ratio influenced the position of the critical state lines for these assemblies. Particle-scale characteristics at the critical state indicate that particles tend to be flat lying, and the obstruction of particle rotation that occurs with longer particles affects their contact mechanics. Lastly, anisotropic coefficients related to aspect ratio were investigated to probe the microscopic origins of the macroscopic behavior. A detailed analysis of geometrical and mechanical anisotropies revealed the microscopic mechanisms underlying the dependency of peak and residual strengths on aspect ratio.

Graphical abstract

Keywords

Ellipsoids; Aspect ratio; DEM; Triaxial compression; Particle shape; Macro-micro response

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