Macroscopic constitutive response of 3D granular assemblies under rotation of principal stress axes

For the quasi-static equilibrium states of granular media, Kishino (1989) developed the granular element method (GEM) to study the flow rule and the stability conditions for granular media: see also Wren & Borja (1997) and Kuhn (1999) who utilized numerical methods similar to the GEM to study the macroscopic constitutive laws for granular media. Also, the entropy estimation of contact forces has been discussed (e.g. Goddard, 2004).