Constitutive model for nonassociative behavior

A simplified approach for the nonassociative behavior of granular (geological) materials is proposed. The basic concept is that the plastic potential can be obtained by controlling or correcting the yield function used for associative plasticity. This is achieved by correcting the hardening, evolution or growth function, which involves only one additional parameter above those for the associative model. Determination of constants and verification with respect to two granular soils tested under a variety of multiaxial stress paths are presented. It is shown that incorporation of the nonassociative behavior through the correction of the growth function yields remarkably satisfactory predictions for volumetric and stress-strain responses of the material response.