Fractal behavior in crushing of rockfill material

Four groups of triaxial test with high confining pressure on Qipei hydropower station bedding material are carried out. Based on the test results of particle size distributions, the fractal model is established, and its fractal behavior in crushing is studied. The results show that particle size distributions after particle breakage of these two kinds of rockfills possess good fractal behavior; fractal dimensions vary from 2.6127 to 2.7232; and the fractal dimensions of bedding material after crushing are less than those of average line. The fractal dimensions increase with the increasing confining pressure in the same density. The increasing trend has stage characteristics: its growth rate keeps slow under low confining pressure; while the grain breakage increases with confining pressure, its growth rate becomes sharp under low confining pressure. The fractal dimensions increase with the density under the same confining pressure. The magnitude of fractal crushing dimensions reflects the particle sizes of breakage and the uniformity of the particle size distributions. The larger the fractal dimension is, the more the quantity of particle breakage is. Besides, there is a close relationship between fractal dimension and Marsal index of particle breakage.