Discrete-element modeling of strain localization in a dense and highly coordinated periodic granular assembly

Strain localization is one of the key phenomena which has been extensively studied in geomaterials and for other kinds of materials including metals and polymers. This well-known phenomenon appears when structure/material is closed to failure. Numerous theoretical, experimental, and numerical studies have been dedicated to this subject for a long while. In the numerical aspect, strain localization inside periodic granular assembly has not been well studied in the literature. In this paper, we investigate the occurrence and development of strain localization within a dense cohesive frictional granular assembly with high coordination number under bi-periodic boundary conditions by Discrete Element Modeling (DEM). The granular assembly is composed of 2D circular particles and subjected to biaxial loading scheme with constant lateral pressure. The results show that the formation of shear bands is of periodic type, consistent with the boundary conditions used. The occurrence and development of the shear band are originated from the irreversible loss of cohesive contacts. The latter is viewed as micro-cracking in the cohesive-frictional granular media, which is highly concentrated in the periodic shear zones and thus related to the strain localization observed at the sample scale. Finally, we also show that the strain localization is in perfect agreement with the kinematic field, displayed in terms of displacement fluctuation.