Role of micromechanics features on stress-level dependency of cross-anisotropic elastic moduli in granular soils

The micro-mechanisms including the nonlinear contact stiffness and the evolution of fabric anisotropy are investigated to tackle the nonlinearity and cross-anisotropy of the elastic stiffness of granular soils. Approximate closed-form solutions are derived for the systematic identification of micro-scale parameters from experimental observations. In the isotropic stress condition, the power relationship of the contact stiffness in the constant fabric condition manifests itself in the stress-level dependency of the elastic moduli. Numerical results relating to the anisotropic stress condition indicate that a wide range of soil elasticity phenomena can be explained if one can account for the evolution of fabric anisotropy induced by the anisotropic stresses, together with the nonlinearity of the contact stiffness. A simple equation of the stress ratio-fabric relationship is provided to capture the effect of the fabric evolution on the elastic response.