Specific features of strain in granular materials

This paper analyses the link between local kinematics and strain tensor defined at a macroscale. The aim of the first part is to analyse the local kinematics variables obtained in a numerical simulation using the DEM. The second part is focused on the analysis of two different approaches to define the strain tensor from local variables. The first approach which only considers relative displacements at the contacts is well known. It is shown that this approach is not usually valid. The second approach is based on the Delaunay triangulation. A decomposition of the local strain is then proposed and it allows the influence of the different mechanisms of the local kinematics (kinematics at contact and displacement of neighbouring particles) to be demonstrated.