Abstract
Strain localization is one of key phenomena which have been studied extensively in geomaterials and for different kinds of materials including metals and polymers. This well-known phenomenon appears when structure/material is closed to failure. Theoretical, experimental, and numerical research have been dedicated to this subject for a long while. In the numerical aspects, strain localization inside the 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 disks and subjected to biaxial loading with constant lateral pressure. The results show that the formation of shear bands is of periodic type, consistent with the boundary conditions. This formation has the origins of the irreversible losing of cohesive contacts, viewed as micro-crackings which strongly concentrated in the periodic shear zones. This micromechanical feature is therefore strongly related to the strain localization observed at the sample scale. Finally, we also show that the strain localization is in perfect agreement with the sample’s displacement fluctuation fields.
Highlights
Strain localization is one of the most typical problems of large deformations in geomaterials
For soils and granular materials, the experimental studies [1,2,3,4,5,6] made it possible to draw several important conclusions which have been listed in [1]: The strain localization in form of shear bands can be observed in most laboratory tests, leading to the failure of geomaterials; The complex regimes of strain localization can arise from particular boundary conditions or loading conditions; A well-marked peak in the stress-strain curve is often considered as a sign of the occurrence of the shear band; The measurements help to identify the shear band orientation
Biaxial numerical simulations by Discrete Element Modeling (DEM) with bi-periodic boundary conditions (PBC) have been successfully performed on a granular sample composed of 22.500 circular particles
Summary
Strain localization is one of the most typical problems of large deformations in geomaterials This phenomenon appears when structure/material is close to failure. The theory of bifurcation is the reference framework for a theoretical consideration of strain localization In this theory, the shear band is treated as a problem of loss of uniqueness of the structure mechanical solution. We tend to establish the linking correlation from the occurrence and development of the shear band to the micro-cracking of cohesive-frictional contact, and the displacement fluctuation field of the granular assembly. This relationship has not yet been fully reported in previous studies. The formation of shear bands within the granular assembly is analyzed and discussed throughout the loading process, in both static (force chains map) and kinematic (displacement fluctuation field) aspects
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