In the Savage-Hutter (S-H) granular flow model

the earth pressure coefficient that is only related to the material property is chosen to describe the internal stresses of the granular flow. However

the constitutive relation of the granular flow is not given in this model. In this paper

an avalanche dynamic model

which can well reveal the constitutive behavior of the granular flow

is developed by introducing the relationship between the stress and the velocity gradient. In order to relax the assumption for lateral stress

the Von Mises criterion

Drucker-Prager criterion

Mohr-Coulomb criterion and Matsuoka-Nakai criterion are combined to yield four expressions of the generalized friction coefficient for describing the moving properties of the granular material. As one of the advantages of the proposed model

the internal mechanism of granular flow is clearly revealed by introducing a simplified constitutive relationship

and the strength parameters used in the proposed model are readily available. The strength parameters derived by Drucker-Prager criterion and Mohr-Coulomb criterion are also analyzed

and the relationship between the generalized friction coefficient and the Lode angle is deduced. It is shown that the numerical simulations of the proposed model agree well with the experimental results.