Abstract:In the present study,a phenomenological constitutive model of viscoplasticity at large strains capable of describing the strain localization problems together with nonlocal approach is developed,which generalizes the classical Perzyna or Duvaut-Lions models to large strains. The nonlocalization for local plastic variable under modeling is implemented by means of numerical weighted operation concerned with a representative size,which characterizes the micro- and meso-effects of material. The model is performed based on a minimum number of hypothesis,including the multiplicative decomposition of deformation gradient,a definition of the elastic domain and finally a penalty-like,viscoplastic regularization of the principle of maximum plastic dissipation. The model is also extended to involve the isotropic and kinematic hardening or softening. Mesh-sensitivity analyses of nonlocalization at large strain along with the refinement of corresponding element size are also discussed. Several illustrative numerical examples that include an unconfined compression test compared with the simulations by FLAC3D and analyses of rheological effect for a typical deep mine after excavation are presented. It demonstrates that the ability of the proposed model to remove the deficiencies of some presently used strain-softening models is acceptable.