Modelling the non-coaxiality of soils from the view of cross-anisotropy

Material anisotropy is widely recognized as the fundamental reason that causes non-coaxiality between principal directions of stress and plastic strain increment. In order to model the non-coaxiality of soils from the view of cross-anisotropy, the anisotropic transformed stress method is introduced. By replacing the ordinary stress with the anisotropic transformed stress, and adopting a normal flow rule in the transformed stress space, non-coaxiality can be reflected simply within the framework of conventional elastoplastic constitutive theory. As an example, the unified hardening model is extended to be cross-anisotropic by this method, and then used to predict the non-coaxiality.