Development of nonlinear cross-anisotropic model for the pre-failure deformation of geomaterials

Nonlinearity and anisotropy of a stress-strain response have been accepted as important factors influencing the pre-failure characteristics of soils. To predict this complex behavior of soils, a simplified soil model was developed using the property of cross-anisotropic elasticity to represent the anisotropic stiffness of soils and the Ramberg-Osgood model to simulate nonlinear stress-strain curves. A hypo-elastic formulation of the stress-strain relationship can describe the directional stiffness as a function of the current stress in a given direction. The model employs the separate formulations of the initial and equivalent elastic moduli for describing the stress-dependency of elastic response of soils. The reliability and usefulness of the model were verified by applications of hollow cylinder tests and triaxial tests on silts. Predictions of soil behavior using this model were compared with representative stress-strain data. The close agreement confirmed that the model reasonably well predicted the nonlinear response of anisotropic deformation at the pre-failure state of soils.