Study of the effects of anisotropic consolidation on granular materials under complex stress paths using the DEM

Abstract

We adopt the discrete element method with a periodic boundary to investigate the comprehensive effects of initial anisotropic consolidation derived from an initial stress ratio ( $$K_{\mathrm{c}})$$ under complex stress paths (b). Both the initial stiffness and deformation mechanisms are systematically analyzed. The dilatancy rate and the stress–dilatancy relationship depend on stress paths and $$K_{\mathrm{c}}$$ . Meanwhile, the distinction between the critical-state mechanical responses under different stress paths also depends on the initial stress ratio. The equation of the relationship between the excess friction angle and peak state parameter is conceptually given, where the coefficients are related to both the initial stress ratio and stress path. At the microscopic level, the properties of contact forces, coordination number, and anisotropies of the assemblies are discussed. The samples with different initial stress ratios exhibit different extents of distinction in terms of various coordinate numbers. The probability density functions of both contact normal and tangential forces are evidently affected by the initial stress ratio, and the effects of the initial stress ratio gradually vanish as shearing proceeds. The strong force chain networks under different conditions of $$K_{\mathrm{c}} $$ and b are explored, showing the comprehensive mechanism of force transmission. At the same strain level, the proportion and the magnitude of strong contact forces strengthen with the improvement of initial anisotropic consolidation, and the initial anisotropic consolidation can evidently improve the ability of the assemblies to cluster along the intermediate principal direction with the increase of b. Different anisotropy parameters show different sensitivities to the initial stress ratio. The fabric-based strength descriptor is linearly correlated to the stress ratio under different $$K_{\mathrm{c}} $$ conditions. The fabric and small-strain stiffness are combined to investigate the macro- and microscopic connections that are subject to inherent anisotropic consolidation as well as the intermediate stress ratio.