Abstract: In order to study the particle breakage rules of rockfill with fractal gradation, a large-scale triaxial test equipment for coarse soil is used to carry out particle breakage experiments under different confining pressures for scaled rockfill materials with different initial gradations. By calculating the change of fractal dimension before and after particle breakage, the effects of stress on the fractal dimension are studied, and the existing particle breakage index B_r is modified. The probability of particle breakage is calculated by using the concept of fractal particle aggregation. The results show that the initial fractal dimensions affect the stress and strain characteristics of the rockfill materials. The fractal dimension and the index of breakage degree are related to the fractal dimension and confining pressure before and after breakage. The particle aggregation can be used to explain the increase of the fractal dimension in fractal gradation. The probability of particle breakage of particle aggregation is independent of the particle size, and the probability of particle breakage increases with the increase of the confining pressure. The probability of particle breakage has upper and lower limits, and the crushing probability is related to the initial fractal dimension D₀.