Stress-induced anisotropy is one of very important characters of soil and also key difference from metal material
which exist in many geotechnical projects. The traditional soil’s constitutive models
which are developed with the isotropic assumption
cannot describe such stress strain relationship. Based on a series of true-triaxial tests under complex stress states
basic anisotropic deformation mechanism and mechanical characteristics of soil are discovered
which will supply enough data for the establishment of anisotropy constitutive model. By considering the stress-induced anisotropy under complex stress states
new anisotropic elastic model and anisotropic plastic model may be developed.