An analysis of the effects of the size ratio and fines content on the shear behaviors of binary mixtures using DEM

Abstract

This study presents an investigation of the effects of the size ratio and fines content on the macroscopic and microscopic shear behaviors of binary mixtures via a series of numerical triaxial compression tests using the discrete element method. The macroscopic behaviors, including the friction angles and stress-dilatancy relationship, and the microscopic behaviors, including the percentage contributions of contact types, average normal contact forces, partial coordination numbers, weak/strong contacts and non-sliding/sliding contacts, are examined. A detailed analysis of the force-fabric anisotropy of the whole contact network enables us to comprehend the mechanism of the critical shear strength independent of the size ratio and fines content. In addition, an inspection of the force-fabric anisotropy of three subnetworks reveals why the percentage contributions of contact types to the critical shear strength vary with the size ratio and fines content. Finally, the geometric anisotropy of the strong and non-sliding subnetwork better explains the mechanism underlying the effects of the size ratio and fines content on the peak and critical shear strengths.