Particle breakage and shape evolution of calcareous and quartz sands under compression

The influences of particle breakage on the mechanical properties of soil are significant. The previous studies mainly focus on the variation of particle size during particle breakage but neglect the change of particle shape. In order to study the evolution of particle breakage, a series of one-dimensional compression experiments are carried out with calcareous sand and quartz sand, and the changes of particle shape are quantified. The results show that the relative breakage index of the two sands increases with the increase of plastic work per unit volume with an obvious hyperbolic relationship. The aspect ratio, sphericity and roundness of the calcareous sand increase with the expanded breakage, but the variation of convexity is unobvious. For the quartz sand, the aspect ratio and sphericity decrease first and then increase, while the convexity decreases to be stable and the sphericity continues to increase. This trend can be well quantified by defining the overall shape value of the samples. In addition, the overall shape value of the calcareous sand shows a hyperbola relationship with the relative breakage, and that of the quartz sand shows a parabola relationship.