Breakage probability of marble spheres under normal, repeated impacts

Abstract

Rock fragmentation is frequently observed during rockfall events. Several selection functions have been proposed via impact tests to describe particle breakage probability. The rock particle breakage probability under repeated impacts is related to the particle size, impact velocity and number of impacts. Quantifying the effects of these variables on the breakage probability of rock particles provides further understanding of how rock particles behave during the impact process, thereby aiding in the design of more reasonable protective measures. In this paper, the results of a comprehensive programme of experiments are presented, in which marble spheres with different diameters were repeatedly impacted against a steel plate under different velocities. Both the diameters of marble spheres and impact velocities were strictly controlled to study the effects of the particle size and impact velocity on the breakage probability. The highest numbers of impacts per marble sphere during the pre-experiments and formal experiments were 200 and 100, respectively, which guarantees a sufficient number of impacts to investigate the influence of the number of impacts on the breakage probability. The results showed that the breakage probability of the marble spheres increased with increasing particle size, impact velocity and number of impacts. Furthermore, a new selection function was proposed to quantitatively describe the breakage probability of rock particles, which enables us to simultaneously consider the effects of the particle size, impact velocity and number of impacts on the breakage probability. Although many factors are considered, the new selection function has only one fitting parameter, and the form is simple. In addition, the calculated results of the new selection function can match the marble sphere experimental results well.