Mechanism of inter-particle friction effect on 3D mechanical response of granular materials

The inter-particle friction is regarded as an important factor that affects the stress and deformation characteristics of granular materials. The existing researches mainly focus on the influences of inter-particle friction on the accumulation characteristics and the macro shear strength, but the mechanism of its influences on the granular materials under the complex stress path has not yet been clarified. A series of true triaxial tests on granular materials are carried out by using the discrete element method (DEM), and the friction coefficient μ is changed to reflect the effects of inter-particle friction on the macro-mechanical properties. The prediction capability of four three-dimensional strength criteria under different inter-particle frictions is discussed, and it is found that the Lade-Duncan and Matsuoka-Nakai criteria have better prediction capability when 0.2<μ≤0.5. In addition, the stress tensors, the distribution of coordination numbers and the fabric tensors of strong and weak contact networks (divided by average contact force) are also studied. The results show that with the increase of inter-particle friction μ, the number of particles forming "force chains" in the strong contact network is basically unchanged, but the normal contact force and normal contact force anisotropy in the strong contact network increases significantly, which mainly causes the enhancement of the macro shear strength. The distribution of coordination numbers of the weak contact network changes greatly with the value of μ, which contributes significantly to the increase of the dilatancy of the particle system.