Quantification of bulk form and angularity of particle with correlation of shear strength and packing density in sands

Abstract

The study presents the quantification of shape parameters in sands. Natural sands, crushed sands, and glass beads are subjected to 2D microscopic and 3D X-ray computed tomographic imaging. Parameters of sphericity, elongation and slenderness are selected for analyzing the bulk forms and roundness is selected to quantify the angularity. Relationship among 2D shape parameters confirms that sphericity, elongation and slenderness are independent with roundness. Critical state friction angles are obtained by a direct shear test and void ratio ranges are measured as well. Both sphericity and roundness denote the strong linearity with void ratio range (emax−emin) bounded 0.15 and critical state friction angle (ϕcs) delineated by 20° at the unity, emphasizing that readily computable sphericity is sufficient to estimate properties of sands even without roundness. The multiple 2D projections of 3D images and their correlation for different orientation support that either bulk form or angularity in 2D images are acceptable enough to establish correlations between shape parameters and properties in sands. It implies that 2D quantification of particle shape is rational and can be used to approximate soil properties without conducting the laboratory experiments.