STRAIN LOCALIZATION ANALYSIS BY ELASTOVISCOPLASTIC SOFTENING MODEL FOR FROZEN SAND

The aim of the present paper is to numerically analyse the behaviour o f frozen sand by using a viscoplastic constitutive model with strain s oftening. A constitutive model has been developed introducing the stre ss history tenser which is a functional of the stress history, with re spect to a generalized time measure. It is shown that Adachi and Oka's model is applicable to the results of triaxial tests on a frozen Toyo ura sand at different strain rates. First, the instability of the mode l is discussed within the framework of bifurcation theory. The model i s then implemented into a FEM code to numerically simulate the behavio ur under plane strain conditions. From the numerical results, it is re vealed that the formation of shear bands is possible and the character istics of strain localization, such as shear banding, depend on the st rain rates.