This title is dedicated to the mechanical behavior and modeling of granular materials: that is, materials made out of assemblies of interacting grains which satisfy the usual laws of mechanics. The book's main focus is devoted to static or dynamic loadings applied to dense materials, although rapid flows and widely dispersed media are also mentioned briefly. Three essential areas are successively covered. The first is: Local variable analysis (Jack Lanier and Fahrang Radjai) - contact forces, displacements and rotations, orientation of contacting particles and fabric tensors are all examples of local variables. Their statistical distributions, such as spatial distribution and possible localization, are analyzed, taking into account experimental results or numerical simulations. The second is: Change of scales procedures (Denis Caillerie, Bernard Cambou) - also known as "homogenization techniques", these procedures make it possible to construct continuum laws to be used in a continuum mechanics approach (the so-called global or macroscopic scale, equipped with usual global variables such as stress and strain) or performing smaller scale analyses (the so-called local scale, equipped with previously defined local variables). The third is: Numerical modeling (Michel Jean including a contribution by Samuel Masson) - several methods designed to calculate approximate solutions of dynamical equations together with unilateral contact and frictional laws are presented, including molecular dynamics, the distinct element method and non-smooth contact dynamics. Numerical examples are given and the quality of numerical approximations is discussed.