DEM investigations on the effects of the intermediate principal stress ratio on the mechanical behavior of a tailings material

The effect of the intermediate principal stress ratio (b) on the mechanical behavior of a tailings material was investigated via the DEM to simulate true triaxial tests. Particle breakage satisfied the octahedral shear stress breakage criterion, and the breakage process employed both the bonded-particle method and the fragment substitution method. The macroscopic behavior of the tailings revealed that when b<0.75, the shear stress ratio is sensitive to b, and when b≥0.75, the effect of b on the shear behavior is minimal. The strain softening or hardening behavior of the sample is determined by confining pressure, with b altering only the degree of this behavior. Conventional triaxial tests underestimate tailings strength in true triaxial stress states. A new strength criterion considering b, based on the power function Mohr‒Coulomb strength criterion, is proposed. The evolution of micromechanical parameters such as the fabric, contact characteristics and anisotropy coefficients was investigated. The results indicate that the resistance provided by nonfailed contacts is the main source of the specimen shear strength. Sliding failure is the primary cause of the reduction in the specimen shear strength. This study elucidates the effects of stress paths on the mechanical behavior of tailings from both microscopic and macroscopic perspectives.