In order to investigate the scale effect of coarse-grained materials

the gradations of Sanbanxi and Shuibuya dam rockfills are statistically analyzed. The Talbot curve can be used as the original “average gradation” for high rockfill dam after analysis. This original gradation curve is scaled utilizing the mixing method which is widely used in projects to compound samples whose maximum particle size distributed from 20 to 180 mm. The relationships between characteristic parameters such as dry density

initial elastic modulus and bulk modulus and the maximum particle size of each group samples are revealed after many sets of numerical experiments which conducted by PFC2D. The results show that the scale effect is related to density control standard. The mechanical parameters are monotone function about the maximum particle size

and the original gradation has 1.5 to 1.6 times anti-distortion capacity of scaled laboratory gradation under the same relative density condition. On the other hand

mechanical parameters are non-monotone function under the same dry density condition. Finally

the mechanical mechanism of scale effect is interpreted with mesomechanics. The particle size and thought are expanded on the basis of PFC2D numerical test.