عنوان مقاله [English]
Many attemps have been made to model the mechanical behavior of soil materials. The assumption that predicting soil plastic behavior in some engineering problems don’t present a significant relation with construction time, has led to the neglect of the time effect in many constitutive models in geotechnical engineering. However, damage due to settlement or instability of excavations and many other such problems are caused by time dependent plasticity behavior of soil. Also in some phenomena such as explosion, earthquake or consolidation, the issue of time is inherently raised. Therefore, it is important to install a time dependent constitutive model in finite element codes that can properly predict the time dependent behavior of structures in geotechnical engineering. In this study, an elastoplastic-viscoplastic constitutive model via UMAT subroutine was installed in the ABAQUS finite element code. By considering the nonlinear elastoplastic-viscoplastic behavior with mixed (kinematic and isotropic) hardening mechanisms, this model removes most of the limitations of the constitutive models already installed in the ABAQUS code. The results of validation under laboratory paths such as creep, relaxation and rate effect indicate the high capacity and capability of the model in predicting the time - dependent behavior of soil.