Non-coaxial plasticity constitutive modeling of sands

The classical coaxial plasticity constitutive models implicate an inevitable limitation as directions for the principal stress and those for the principal plastic strain rate are always coaxial.They are not capable of simulating non-coaxial phenomena during the rotation of principal stress axis.A 3D non-coaxial plasticity constitutive model for sands with a modification of Lode angle dependent shape function is introduced to describe the non-coaxial behavior under the principal axes rotation.A series of numerical simulations of true triaxial,simple shear and hollow cylindrical torsional shear tests is performed.The results show that the proposed constitutive model can better describe the deformation characteristics of sand in true 3D state,and predict variations of the principal plastic strain rate directions with the principal stress directions reasonably.