Effect of particle size and particle size distribution on critical state loci of granular soils

The critical state soil mechanics captures a wide range of stress-strain behaviour in an understandable context. It provides a conceptual framework for predicting soil behaviour and that is why the critical state is a central part of most advanced constitutive models. This study aims at quantifying the effects of both particle size, and particle size distribution on the critical state loci. Two soils, a natural soil and a tailings, were selected and CSLs were identified for twelve uniform and well graded particle size distributions. Mineralogy and particle shapes were rigorously quantified to ensure other factors are not influencing the results. Particle size has a small influence on the CSL in the sand to gravel range, but silts can have a significantly different CSL. In both natural soil and tailings, particle size distribution appears to have a significant influence on the CSL in e - log p' space and little influence in q - p' space. Well graded soils have lower CSLs compared to uniform ones, that are generally parallel to the CSLs of their dominant constituent, with the exception of convex distributions where progressively finer particles in larger proportions can form structures noticeably less compressible than any of their constituents.