Particle breakage and the critical state of sand

Soil particles break during shear, with the intensity of the breakage depending on the stress level amongst other factors. Particle breakage has important implications for the soil׳s critical state, which is an input to the majority of advanced constitutive models. This work examines a micromechanical framework where particle breakage shifts down the critical state locus in void ratio versus mean effective stress space without changing its slope. The framework assumes that detectable particle breakage in sand does not occur unless the contraction potential of the material, solely by the sliding and the rolling of the particles, is exhausted and a soil specific stress level threshold is surpassed. A series of triaxial compression tests conducted to investigate the validity of the framework is presented. It is shown that particle breakage is a factor, working alongside dilatancy, imposing additional compressibility on the soil.