Abstract: Three-dimensional particle flow code(PFC)is adopted to simulate the true triaxial tests of rockfill. Not only the macro stress and deformation characteristics of the rockfill under three-dimensional stress conditions are researched, but also the micro and macro parameters are then linked with each other in order to further improve the study of rockfill. In the process of the test, the ratio of intermediate principal stress is fixed. By comparing the results of rockfill true triaxial test based on PFC and the results of true triaxial test in laboratory, we find that the PFC can suitably simulate the mechanical properties of rockfill. The PFC numerically experimental results indicate that the intermediate principal stress has a remarkable influence on the strength and deformation of rockfill under the three-dimensional stress condition. When stress ratio parameter change from 0 to 1 , the intermediate principal stress surface compresses firstly and inflates later; the minor principal stress surface is always on the compression state. The intermediate principal stress is influences on the internal friction angle, the elasticity coefficient and the Poisson's ratio. In a mesoscopic view, we find that the higher confining pressure is, the higher value of b is, the greater particle coordination number is, and the smaller porosity factor is. The rockfill macroscopic stress and deformation phenomena are explained from microscopic angle.

Key words: rockfill, true triaxial test, particle flow code(PFC), numerical simulation, intermediate principal stress