Laboratory investigation on the single particle crushing strength of carbonate gravel incorporating size and shape effects

Particle strength is one of the critical factors that causes the degradation of the mechanical behaviour of crushable soil. Because of the complexity of particle shape, its effect on particle strength has not been completely understood. In this study, single particle crushing tests were performed on carbonate gravel particles with three size fractions (i.e. 5–10 mm, 10–15 mm and 15–20 mm) and three shapes (i.e. blocky, rodlike and flaky), using a PartAn 3D Maxi large particle size and shape analyser to obtain the shape characteristics of the particles. The determination of crushing strength for particles with complex shapes was discussed, and it was found that it is appropriate to use the area equivalent circle diameter to obtain the crushing strength. The influence of particle size and shape parameters, including the elongation index, flatness index, intercept sphericity, circularity and convexity, on the crushing strength were identified, and an index termed the form factor considering dimensions in three directions was proposed to describe the effect of particle shape. Based on this form factor, a probabilistic model was established to predict the distribution of crushing strength of carbonate gravel particles with various sizes and shapes. The proposed model could be used in the discrete-element method to consider the influence of shape in addition when evaluating particle breakage.