Crushing and fractal behaviors of quartz sand-gravel particles under confined compression

A confined compression test was used to investigate the crushing behaviors of coarse quartz sand and fine gravel particles under high compressive stress,and their fractal crushing was studied based on the fractal concept and the measured data of particle-size distribution.It was shown that the quantity of particle breakage increased with the increase of compressive stress and was related to the particle size.With the increase of quantity of particle breakage,the angles of friction increased for coarse sand,increased at first and then decreased for fine gravel.Both had the tendency finally to an unvaried value when the quantity of particle breakage was large enough.It was shown that the particle-size distribution after particle breakage exhibited a statistical fractal feature.The magnitude of fractal crushing dimension reflected the variation of quantity of particle breakage.Large fractal crushing dimension corresponded to large quantity of particle breakage.There was a close relationship between fractal crushing dimension and Hardin index of particle breakage.The relationship between fractal crushing dimension or Hardin’s index and compressive stress could be expressed by hyperbolic curves or semilogarithmic linear curves.As a result,the fractal crushing dimension and Hardin index could be evaluated as long as compressive stress and parameters of soil particles were obtained.The fractal crushing dimension might be useful indicator for quantitative analysis of the particle breakage of granular materials.