Sample size effect on DEM simulations of binary mixture

Abstract

This paper presents a study of the effect of sample size on packing density and the mechanical behavior of a binary granular mixture of ellipsoids subjected to rigid and periodic boundaries. The binary mixture contains two similar ellipsoids of different sizes. Since they are similar, the particle shape of these binary mixtures can be denoted by elongation, the ratio between the major length and minor length of an ellipsoid. Elongation of 1.5 is chosen in this study. The large particle is 5 times the size of the small particle. Samples of various weight fraction of small particles (fine content) have been created. The generated samples are very dense that are close to the densest packing. The void ratio (packing density) of the binary mixtures is related to fine content as expected. The sample size effect on void ratio was found in rigid boundary but not in periodic boundary as expected. Triaxial simulations were carried out to determine the peak shear strength and the properties at critical state. Sample size affects more on peak shear strength than critical state void ratio. Although small sample size can be used with periodic boundary to avoid boundary effect, the observed unusual peak strength behavior requires further investigation.