Babak Ebrahimian - Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran
Ali Noorzad - Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran
Ahmadreza Mahboubi Ardakani - Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran

This paper presents numerical investigations of strain localization in a plane granular layer under monotonic shearing. For this purpose, Finite Element (FE) formulations in the Updated Lagrangian (UL) frame are used. An elasto-plastic Cosserat continuum approach is adopted to describe the essential properties of dry and cohesionless granular material like sand. The constitutive model can capture the influences of pressure, void ratio, mean grain diameter and rotation resistance of grains on the evolution of stresses and couple stresses. Due to the presence of a characteristic length of micro-structure in the form of mean grain diameter, the model can simulate the formation of shear bands with a certain thickness and the related size effects. FE calculations show that the location and thickness of induced shear bands are mainly affected by the boundary conditions of the entire system. According to the obtained results, it is revealed that the shear band location is different in an infinite or finite shear layer depending on the adopted boundary constraints.

Shear layer, Strain localization, Cosserat material, Granular body, Finite Element analysis.