Gradation design method for rockfill materials based on fractal theory

According to the fractal theory, the fractal distribution formula of gradation for rockfill materials is deduced. The field gradation data of six dams with clay core and five 200 m-high CFRDs are used to verify the relevant achievements. The result shows that the correlation coefficient is basically above 0.95. Compared to the uneven coefficient C_u and curvature coefficient C_c, the particle fractal dimension can objectively reflect the average characteristics of rockfill gradation. The relationship between gradation (particle fractal dimension) and density is studied by conducting the extreme dry density tests on scaled rockfill materials of different source rocks from dacite, tuff and migmatite. In combination with the field gradation rockfill data of four dams, including Shuibuya Dam, the conclusion is drawn that the gradation is considered as the main factor affecting the compaction properties of rockfill. By means of the relationship among C_u, C_c and the particle fractal dimension, the favorable gradation scope is deduced for the coarse-grained materials such as the rockfill and transition materials, providing the basis for the gradation design and optimization of rockfill materials.