ABSTRACT
Non-coaxiality, which means the non-coincidence of the principal stress tensor and the principal plastic deformation-rate tensor, is an important property of granular materials and has been demonstrated by a variety of experiments. Hence, it is important for constitutive models to describe non-coaxiality. The physically-based kinematic models (Mandel, 1947, De Josselin de Jong, 1958, Spencer, 1964, Mehrabadi and Cowin, 1978,Anand, 1983, Nemat-Nasser, 2000, Jiang et al., 2005a) describe plane plastic flow of granular materials with two kinematic equations governing the velocity field.
