Discrete element methods (DEM) constitute an important tool for the study of granular matter and divided materials or structures. Basically DEM model a material or a structure at the grain scale and are able to describe various complex behaviors (flow, localization of deformations, fracture, dissipation, etc) which can't be properly represented by continuum approach even with advanced constitutive model based on a huge number of parameters.

The present work aims to check for the effectiveness of the shear reinforcement on masonry panels by using a composite made by the union of unidirectional hemp fibers with hydraulic mortar, specific for strengthening interventions on masonry. The study deals with the simulation of in-plane shear action on masonry walls through diagonal compression tests on externally reinforced masonry panels. The first experimental results have already shown a significant increase in shear strength and stiffness compared to the samples tested without reinforcement. The panels have been subsequently discretized in the computer code LMGC90. Particularly, the model proposed for the composite strips takes into account only the fibre tensile failure mode with the hypothesis of perfect adhesion between reinforcement and masonry support. The numerical analysis are in good agreement with experimental data, showing the validity of this first numerical modeling approach for the reinforcement.

A jointed rock mass geometrical model is built, based on the fracture systems characteristics obtained from field measurements. This model is composed of three-dimensional polyhedra interacting with each other by contact laws, in the frame work of the Non-Smooth Contact Dynamics method. The stability assessment of the walls of a stone quarry in France is presented, as a case study.

We rely here on a non-smooth contact dynamics (NSCD) approach to treat particle collisions in a direct numerical simulation of a dense particulate flow. Interactions between particles are considered by a non-smooth formulation of particle dynamics at the microscopic scale, which enables one to straight forwardly implement complex contactlaws. The hydrodynamic coupling is achieved by a distributed Lagrange multiplier/fictitious domain (DLM/FD) method . As a preliminary step, the relevance of our NSCD-DLM/FD method is assessed by comparing results of 2D sedimentation simulations with those obtained with a usual molecular dynamics collision model. Then, we use it to investigate how a fully immersed granular packing collapses depending on its initial particle volume fraction, providing clues on the micro-rheology of dense particulate flows.

The present paper proposes an extension of the classical discrete element method used to study third body flows. Based on the concept of the tribological triplet proposed by Godet and Berthier, the aim of this work is to enrich description, by accounting for the deformation of the first body and investigating its influence on third-body rheology. To achieve this, a novel hybrid approach that combines continuous and discontinuous descriptions is used. To illustrate the advantage of such modeling, comparisons with the classical approach, which considers the first body as rigid, are performed in terms of macroscopic friction coefficient and velocity and stress profiles.

This book brings together various methods and skills for discrete numerical modeling of granular media. Four basic methods (molecular dynamics, contact dynamics, quasi-static and event driven) are presented, followed by various methods for sample preparation, boundary conditions and the choice of control parameters. Complex compositions (particle shapes and size distributions) and interactions (cohesive, hydrodynamic, thermal) have been extensively discussed.