INSTABILITY OF AN ELASTOVISCOPLASTIC CONSTITUTIVE MODEL FOR CLAY AND STRAIN LOCALIZATION

A viscoplastic strain softening model is derived and the instability o f the model during the creep process is discussed. It is found that th e proposed viscoplastic model is capable of describing plastic instabi lity. The applicability of the model is evaluated with the results of experiments on Osaka alluvial clay. Finally, we numerically analyze th e behavior of the clay in undrained plane strain compression tests by the finite element method, considering a transport of pore water in th e material at a quasi-static strain rate. The numerical results show t hat the model can predict strain localization phenomena, such as shear banding.