Micromechanism study on the influence of particle deposition angle on mechanical properties of sand

To gain a deeper understanding of the fundamental characteristics of internal forces and deformations in the directional distribution of granular materials, it is necessary to investigate the directional distribution of particles on the mechanical properties and microstructural evolution process of the soil. The discrete element particle flow program PFC^3D is used to construct the particle with the same aspect ratio, convexity, and sphericity as the binary images, and the specimens with directional particle distributions of 0°, 30°, 45°, 60°, and 90° are generated. Furthermore, the quantitative correlations between the constitutive parameters and the deposition angle are examined. The results show that the shear strength and shear expansion of the soil increase with increasing deposition angle. With an increase in axial strain, the dominant direction of contact points and the direction of force chain and normal contact force rotate counterclockwise. In the critical state, the microstructural direction of the specimens with different deposition angles is approximately the same, which is primarily along the direction of 45° + ϕ_cs. The critical friction angle decays as a power function with the increase of deposition angle in undrained tests. The critical void ratios of the specimens with different deposition angles under drained tests decay linearly as the deposition angle increases. The critical mechanical coordination number decays exponentially with an increase in deposition angle under undrained tests. The conclusions mentioned above serve as a guide for revising the constitutive equations for specimens considering the microscopic behavior.