Effect of fluctuation of current void ratio on the shear zone formation in granular bodies within micro-polar hypoplasticity

The paper focuses on the effect of the distribution of the initial void ratio and fluctuations of the current local void ratio on the evolution of the internal shear localization within a granular body under plane strain conditions during a compression test. For a simulation of the mechanical behavior of a cohesionless granular material during a monotonous deformation path, a micro-polar hypoplastic constitutive was used which takes into account particle rotations, curvatures, non-symmetric stresses, couple stresses and the mean grain diameter as a characteristic length of micro-structure. The proposed model captures the essential mechanical features of granular bodies in a wide range of densities and pressures with a single set of constants. For the calibration of the constitutive constants, the data of a medium quartz sand are used. The effect of various stochastic distributions of the initial void ratio (both spatially correlated and non-correlated ones) on shear localization in the granular specimen was investigated. In addition, the calculations were carried out with different amplitudes and frequencies of fluctuations for the change of the current void ratio.