Effect of particle size ratio and volume fraction on shear strength of binary granular mixture

Abstract

This paper deals with the mechanical properties of a binary granular mixture: a mixture of large and small frictional particles. The binary mixture is characterized by the particle size ratio (α = DL /DS ≥ 1), where DL and DS denote the diameter of large and small particles, and the volume fraction of the small particles WS. In order to eval- uate the shear strength of such a system, a transition range (W a S ≤ WS ≤ W b ), where W a and W b S are minimum and maximum WS values of the range, respectively, is defined as the range in which the interaction between the small and the large particles cannot be negligible. Then a simplified pack- ing structure model is proposed to estimate W a S and W b S with respect to α. A series of 2D Discrete Element simulation and physical experiment proved that the proposed method can successfully describe the shear strength transition of the densely packed granular material both in 2D and 3D. As a general trend, it also turns out that the contribution of the small particles cannot be negligible even in their small con- tent, and the contribution of large particles disappears when their average spacing with respect to the small particle size is around 2 both in the simulation and the experiment.