Effect of Sample Preparation Technique on Strain Localization of Dense Sand Under Biaxial Test Condition

During the process of shearing, deformation of granular materials like dense sand is often noticed to concentrate within a narrow zone, commonly referred to as shear bands. Various studies show that the formation of shear band is influenced by the internal inhomogeneity of the granular assembly. Owing to various ways of specimen generation, internal inhomogeneity arises in sample while performing laboratory experiments or carrying out micromechanics-based simulations employing discrete element methods (DEM). Hence, understanding the effect of inhomogeneity, resulting from such sample generation techniques, on the formation of shear bands becomes imperative. In the present study, DEM-based biaxial test simulations have been performed on the dense sand specimens, which have been prepared following two sample generation techniques. Biaxial shearing of these specimens has been conducted by adopting a stress-controlled flexible boundary. It has been noticed that dense specimen shows buckling and bulging-type deformation accompanied with the formation of localized shear bands. The initiation and propagation of persistent shear bands have been analyzed from the spatial variation of porosity and particle rotations within the specimen. The position of shear band within the specimen differs due to presence of different initial inhomogeneity within the particle packing arrangement arising due to variation in the specimen generation process.