Experimental Micro-Macromechanics: Critical States of Round/Angular Granular Mixtures

This paper comprehensively investigates the influence of mixing angular particles on macroscopic shear strength and microscopic particle motion in granular mixtures. Circular and hexagonal particles of two sizes were used, and varying proportions of angular content were achieved by introducing hexagonal particles into circular samples. Biaxial shearing tests were conducted under three different confining stresses. The results revealed that an increased angular content within the granular mixtures resulted in enhanced interlocking configurations, leading to higher critical-state strength and dilation. This highlights the crucial role of particle angularity in governing the macroscopic characteristics of such granular mixtures. At the microscopic level, an increase in angular content generally caused a decrease in overall particle rotations within the mixtures. Specifically, circular particles experienced significant reductions, while hexagonal particles showed negligible effects, suggesting round particles were more susceptible to angular particles, restricting their rotational movement. Conversely, hexagonal particles were less influenced, indicating a unidirectional restriction. This study deepens our understanding of particle interactions and mechanical responses in granular mixtures, highlighting the significance of angular content in influencing shear strength and particle motion.