Modifications in anisotropic critical state theory to account for nonproportionality between fabric tensor and plastic strain rate direction

In anisotropic critical state theory (ACST) for granular media, the role of the fabric anisotropy variable (FAV) A that relates the fabric tensor F with the plastic strain rate direction n is of cardinal importance. Yet, the original definition of A can acquire the same value for various F given n, and vice versa, because it does not account for the nonproportional components of F in reference to n. This inadequacy is addressed by novel redefinitions of A which maintain its predetermined role within ACST, while they are simple enough to be tested in future research when simulating the response of granular media with strong nonproportionality between F and n, with either discrete element method (DEM) or plasticity constitutive models.