Microscopic mechanical analysis of K0 of granular soils with particle size distribution and rolling resistance effects

The coefficient of lateral earth pressure at rest, K₀, is an essential parameter for analyzing earth pressure distribution and the safe reliability of structures in geotechnical engineering. This paper presents a series of numerical one-dimensional compression tests on granular soils with particle size distribution (PSD) and rolling resistance (RR) effects using a real-particle 3D discrete element model. The corresponding macro–micro behaviors are investigated in a parallel way. Both PSD and RR affect K₀ and the related compression characteristics. A higher coefficient of uniformity (C_u) or rolling resistance coefficient (μ_r) results in a monotonic decrease in the mean coordination number, and too much consideration of RR makes the mean coordination number less realistic in a particle system. The influence of PSD is more sensitive to the local-ordering structure and contact force network than the RR. The inhomogeneity of normal contact forces enhances as C_u increases and slightly reduces as μ_r increases. The strong contacts are much more anisotropic than the weak ones. Specimen with lower C_u or higher μ_r induces higher anisotropy and more strong contacts during compression, in which a lower K₀ is measured. A unique macro–micro relationship exists between K₀ and deviatoric fabric when strong contacts are considered only.