Abstract: The material strength is directly affected by the random distribution of the size, shape, orientation and spatial location of internal microcracks. This study aims to investigate the statistical relationship of the strength of rockfill particles with respect to size and strain rate under quasi-static condition. The assumption is made both the size and spatial location of microcracks followed the power-law distribution. A rational link is established between the compound parameters, which consist of the cumulative damage probability and volume of the particles and the crushing strength within the framework of the weakest chain theory. From a microscopic perspective, the strength of microcracks in particles increases with the strain rate. The effect of strain rate leads to a reduction in the failure probability per unit volume. Simultaneously, the spatial location distribution of microcracks becomes sparse, and the size effect on particle strength weakens. The results of the single particle crushing tests show that as the loading rate increases, there exists a gradually decreasing power index of spatial location distribution, which allows the particle compound parameters to converge on the master curve determined by the weakest chain statistical model.

Key words: particle strength, size effect, strain rate effect, statistical model