Coupled effects of particle overall regularity and sliding friction on the shear behavior of uniformly graded dense sands

Particle morphology has been regarded as an important factor affecting shear behaviors of sands, and covers three important aspects, i.e. global form (overall shape), local roundness (large-scale smoothness), and surface texture (roughness) in terms of different observation scales. Shape features of different aspects can be independent of each other but might have coupled effects on the bulk behavior of sands, which has been not explored thoroughly yet. This paper presents a systematic investigation of the coupled effects of the particle overall regularity (OR) and sliding friction on the shear behavior of dense sands using three-dimensional (3D) discrete element method (DEM). The representative volume elements consisting of ideal spheres and irregular clumps of different mass proportions are prepared to conduct drained triaxial compression simulations. A well-defined shape descriptor named OR is adopted to quantify particle shape differences of numerical samples at both form and roundness aspects, and the particle sliding friction coefficient varies from 0.001 to 1 to consider the surface roughness effect equivalently in DEM. The stress-strain relationships as well as peak and critical friction angles of these assemblies are examined systematically. Moreover, contact network and anisotropic fabric characteristics within different granular assemblies are analyzed to explore the microscopic origins of the multi-scale shape-dependent shear strength. This study helps to improve the current understanding with respect to the influence of the particle shape on the shear behavior of sands from different shape aspects.