Abstract: The existing researches indicate that the mechanical properties of rockfill materials are significantly affected by the particle crushing. In order to reproduce the fundamental features of particle breakage, the changes of the particle size distribution (PSD) have to be described in mathematical form, i.e., to track the evolution of the PSD. This is difficult for the triaxial test processes due to the measurability limit of particle breakage. The single particle strength of the rockfill is measured and the crushing sample is sieved. The results show that the strengths of particles obey the Weibull statistics, and that the fractal distribution is found for PSD of crushed aggregates. Based on those findings, the changes of PSD can be described during the triaxial test process, the breakage of the triaxial tests is simulated, and the results reveal that the breakage process well agrees with the experimental data.