Sustainability of internal structures during shear band forming in 2D granular materials

Abstract

The shear band issue in frictional granular materials has attracted many concerns and perspectives at the micro- and meso-scale have been involved to analyze this problem. At the microscopic level, the contact sliding is associated with the plastic dissipation; while at the mesoscopic level, force chains and loops will change in geometry and topology as deviatoric loads are applied. This paper concerns the unstable behaviors from these two scales which could be regarded as loss of sustainability of internal structures, and tries to relate the microscopic sliding and the mesostructural evolutions. Firstly the heterogeneity generation is identified for the granular assembly subjected to the biaxial loading using DEM. Then the internal structure evolutions and interrelationships are investigated, leading to these main conclusions: sliding contacts are not within force chain structures but will be strongly influenced by the force chain buckling; exchanges within grain loops appear during the whole loading process and differ for domains inside and outside the shear band; the topological dilations are related to the higher probability of contact sliding. In brief, the microscopic dissipative behavior as the contact sliding plays an important role in the mesostructural organizations.