Constitutive model of tailings sand plays an important role in the numerical simulation and security evaluation of tailings dam. However

current researches focus on nonlinear elastic model such as Duncan-Chang model

but less on elastoplastic model. A modified generalized plasticity model considering the stress-strain property of tailings sand is proposed to describe the mechanical characteristics of tailings sand. The constitutive model is developed in ABAQUS with user defined material subroutine UMAT and explicit stress integration of Runge-Kutta method. Finally

the modified model is verified in ABAQUS by triaxial test simulation. The deviatoric stress curve shows that the results of finite element method can reflect the influence of confining pressure on stress-strain relationship. And the shear strength gradually increases with strain increases

followed by strain softening after reaching the peak strength. Volumetric strain calculation results show that the generalized plasticity model can well describe the volumetric strain development

which is in good agreement with the experimental curve. Meanwhile

finite element computation data match well with test data

and the theoretical value. The research results can be further used in the stress-strain analysis and security evaluation of tailings dam.