Three-dimensional discrete element simulations of inherently anisotropic granular materials subjected to circular rotational shear stress path

Abstract

Understanding the response of sand to complex loading conditions is vital for practical geotechnical engineering. Circular rotational shear is a special stress path where the magnitudes of three principal stresses vary following a circular stress trajectory in the π-plane with their directions fixed. Although experimental studies under such stress paths are limited, the discrete element method appears to be an appealing approach to examine the response of granular materials to varying complex loading paths in numerical “virtual” tests. This study presents comprehensive numerical simulations of granular samples subjected to a circular stress path under varying conditions, including samples prepared with different bedding-plane angles and densities and subjected to different stress ratios. Both macroscopic and microscopic behaviors are presented and interpreted. A contact-normal-based fabric tensor is adopted in a detailed analysis to measure the internal structure of the granular assembly. The fabric, strain, and strain increment tensors are decomposed with respect to the stress tensor, and the evolutions of these components are presented along with the key influential factors. The results obtained in this study provide useful physical insight for the development of constitutive models for granular soils under general loading conditions.