To describe the influence of intermediate principal stress on the mechanical behavior of overconsolidated soil

a novel elastic-plastic constitutive model was proposed to produce the characteristics of over consolidation and stress-induced anisotropy of soil. The shape function   

which can uniformly describe the four yield criteria of Mohr-Coulomb

Drucker-Prager

Lade-Duncan

and Matsuoka-Nakai

is introduced into the subloading yield surface model to modify the M value so that the M value can change with Lode Angle in the new model. The plastic deviatoric strain increment was selected as the iteration variable. The stress integration algorithm of the new model was achieved by Newton-Raphson iteration

and the UMAT subroutine was written. The new model has been implemented into a large commercial finite element software ABAQUS. The results show that: 1) The new model can simultaneously characterize the over consolidation

dilatancy

and stress-induced anisotropy of soil

and the predicted results are in a good agreement with the experimental data. 2) The physical meaning of the new model is clear and simple

which is convenient for engineering promotion and application; 3) The stress integration algorithm of the new model has a fast convergence speed

fewer iterations per incremental step

high convergence accuracy

and robustness.