Size distribution, morphology and fractal characteristics of brittle rock fragmentations by the impact loading effect

Abstract

The dynamic fragmentation of three types of brittle rock is examined in this paper by impact experiments using the split Hopkinson pressure bar system. The generalized extreme value distribution is used to characterize the size distribution of the fragments. The results indicate that the slate particles are shaped as a sheet, sandstone fragments appear as irregular prisms, and granite is shaped as a fine grain. Granite is the specimen most easily broken followed by sandstone and slate. The NUM-based cumulative frequency distribution curve moves toward the left as the impact stress increases. Fitted curves of the size distribution of the granite fragments are more intensive at the section of relatively small particle size and become sparser when the particle sizes increase, contrary to the sandstone and slate. Moreover, the aspect ratio of the granite fragments is smaller and more intensive than the other two specimens, even under simple impact conditions. Peak values in the probability density function curves of the fragment size are consistent with the theoretical results. Fractal theory is further used to study the fragmentation features. The results show that the fractal dimension value increases with increased specimen stress, and the fragments of slate and sandstone have smaller values than the granite within a certain range. Additionally, the value is also limited by the fragment size distribution, and the fractal dimension value increases as the dominant fragment size decreases.