Abstract: In the process of rotation of the orientation of principal stress, the non-coaxial phenomenon exists between the orientations of the principal stress and plastic strain rate. However, the traditional constitutive theory could not reflect the non-coaxial phenomenon and its influence on the relationship between stress and strain. The yield vertex non-coaxial theory is adopted into a strain softening coaxial model to research the non-coaxial phenomenon and its influence in the numerical simulations of simple shear test on dense sand. Comparison between numerical result and test result suggests that the non-coaxial model could reflect the non-coaxial phenomenon and its influence reasonably, and also, the roles of non-coaxial model are considerably influenced by static lateral pressure coefficients, vertical stress and flow rules.

Key words: non-coaxial, constitutive theory, strain softening, simple shear test, numerical analysis