Development of a generalized plasticity constitutive model in the framework of the multilaminate method and its evaluation in geotechnical numerical analyses

A generalized constitutive model is presented in the framework of the multilaminate method in this paper. This model does not need to explicitly define the yield and plastic potential surfaces. In this framework, the constitutive relations between stresses and strains in the form of volumetric and deviatoric components are defined on several planes in various directions, called microplane. A new volumetric–deviatoric stress space is defined on the microplanes. The new constitutive model uses a new stress space in which stress–strain relations are defined in a scalar form instead of a tensor form, and this potentially enhances the computational efficiency of the model. The proposed model captures induced anisotropy, including principal stress axes rotation effects, through microplane-specific strain histories and hardening laws. While inherent anisotropy is not addressed here, the framework allows its incorporation via directional microplane properties without changes in formulation. The results predicted by the new constitutive model for several types of clay and sand in drained and undrained conditions have been validated with experimental data. The new constitutive model has been implemented in OpenSees software, and the Mahabad earth dam is analyzed by it in a steady-state condition which demonstrates the practical application of the model.