Research on the Particle Breakage of Rockfill Materials during Triaxial Tests

Particle breakage modifies a rockfill structure, influencing its dilatancy, friction angle, strength, and permeability, as well as generating creep deformation, wetting deformation, and residual strain under a seismic load. However, the breakage laws of rockfill during shearing remain unclear. This paper investigates the particle breakage of the basalt rockfill that is used in the Gushui concrete face rockfill dam during specimen preparation, consolidation, and drained triaxial shearing. The results indicate that the hammer compaction during specimen preparation generates a considerable amount of particle breakage, whereas isotropic consolidation generates negligible particle breakage. Under a low confining pressure (100 kPa), rockfill particle sliding and roll over are loosely constrained, and negligible particle breakage occurs during triaxial shearing. Under a high confining pressure (greater than 500 kPa), rockfill particle sliding and roll over are more constrained. Thus, the contact force significantly increases and significant particle breakage occurs. During triaxial shearing, larger diameter particles break first and smaller diameter particles begin to break as the confining pressure increases. The percentage of particles with diameters below 0.25 mm always increases with increasing shearing strain, and the amplitude increases with increasing confining pressure. Particle breakage during shearing in the triaxial test is affected by both the shear strain and stress. Additionally, the relationship between the relative particle breakage index and plastic work can be simulated with a hyperbolic formulation.