Abstract: 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 g（θ）  , 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 θ  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.

Key words: overconsolidated soil, anisotropy, unified yield criterion, subloading yield surface, stress integration algorithm