Linking shear strength to granular skeleton state of continuously graded coarse-grained soils: Insights from discrete element modelling

Abstract

Particle size distribution (PSD) affects the strength behavior of continuously graded coarse-grained soils by modifying the granular skeleton state. However, due to the lack of a proper indicator linking the skeleton state to PSD, the quantitative relation between shear strength and granular skeleton state remains unexplored. Based on a concept of effective dominant skeleton size ded in multi-sized particle packing model, this study attempted to link granular skeleton state with friction angles of continuously graded coarse-grained soils. Using the discrete element method (DEM) and an improved PSD model, dense packing specimens with 36 PSDs were generated and conducted for biaxial tests. The results indicate that ded has a strong correlation with the size and stress distribution of active particles, i.e., ded can reflect the overall size level of skeleton particles in continuously graded granular soils. A definite semi-log linear correlation between φp and ded was revealed, wherein fitted intercept A and slope B were found to be related to particle-scale strength properties. According to the similarity of φp-di relation in uniform-sized particles and φp-ded relation in continuously graded soils, a method for estimating φp of coarse-grained soils with any PSD was proposed and validated by a series of experimental direct shear tests.