Shear behaviours of cohesionless mixed soils using the DEM: The influence of coarse particle shape--颗粒学报PARTICUOLOGY

Zhu, Y., Gong, J., & Nie, Z. (2021). Shear behaviours of cohesionless mixed soils using the DEM: The influence of coarse particle shape. Particuology, 55, 151-165. https://doi.org/10.1016/j.partic.2020.07.002

Shear behaviours of cohesionless mixed soils using the DEM: The influence of coarse particle shape

Yangui Zhu, Jian Gong, Zhihong Nie ^*

School of Civil Engineering, Central South University, Changsha 410075, China

10.1016/j.partic.2020.07.002

Volume 55, April 2021, Pages 151-165

Received 3 February 2020, Revised 21 June 2020, Accepted 7 July 2020, Available online 3 August 2020, Version of Record 3 February 2021.

E-mail: niezhih@csu.edu.cn

Highlights

• An equation was proposed to predict initial void ratios of samples.

• Effect of coarse particle roundness on friction angles of mixed soils was studied.

• Coarse particle roundness hardly affects the classification of mixed soils.

• Main forms of coarse–coarse contacts were revealed at the critical state for FC = 30%.

• Roundness and rolling resistance affect mixed soil strengths by various mechanisms.

Abstract

The coarse particles in mixed soils can be cobbles or gravels, with the main difference being their roundness (an indicator describing particle shape characteristics at an intermediate scale). The influence of coarse particle shape (i.e., roundness) on the macroscopic and microscopic shear behaviours of cohesionless mixed soils with various fines contents (FCs) was investigated via the discrete element method in this study. The shapes of coarse particles were formed using the rotation-invariant spherical harmonic method proposed by previous investigators. An equation was proposed to predict the initial void ratios of samples in this study. A decrease in the roundness of coarse particles can increase the peak friction angle (FC ≤ 40%) and critical friction angle (FC ≤ 30%). As the roundness of coarse particles decreases, the peak dilatancy angle initially increases and then decreases (FC ≤ 20%). Furthermore, it was found that the roundness of coarse particles hardly affects the classification of cohesionless mixed soils, as determined by probing the percentage contributions of coarse–coarse, coarse–fine, and fine–fine contacts. When cohesionless mixed soils change from an underfilled structure to an interactive-underfilled structure at the critical state, the main forms of coarse–coarse contacts were discovered. Additionally, the force-fabric anisotropy mechanisms of the influences of the roundness and rolling resistance coefficient of coarse particles on the shear strengths of cohesionless mixed soils were found to be different.

Graphical abstract

Keywords

Cohesionless mixed soils; Particle shape; Roundness; Shear behaviours; Discrete element method

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