1. INTRODUCTION Mechanical particle crushing is used in civil engineering, powder technology and mineral industry. The most elementary crushing event is the crushing of a single particle subjected to highly compressive stresses. Single- particle compression tests, in which an individual sand grain or rock stone is vertically compressed between two horizontal platens, are often used to study crushing at the particle-scale [1-3]. Crushing depends on particle size, shape and coordination number [4-6]. Effect of particle size. Because larger particles tend to have larger internal flaws than smaller ones, particle strength decreases with particle size [7]. Hiramatsu [8] studied the stress distribution in a single particle subjected to a concentrated load by means of photoelastic experiments and mathematical analysis. They found the analytical expression of stress for spherical particles. Then based on the results of compression tests, they calculated the tensile stress in a piece of rock by  ! = .    , (1) where  ! if the tensile stress at failure,  ! is the peak compressive force applied and  is the rock particle size. Lee [9] conducted a series of compression tests of individual particles and proposed an equation to describe size effects during crushing:     =  ! , (2) Where  is a material constant variable, and  represents the size effect. Effect of particle shape. The shape of a particle is characterized by sphericity, roundness and Discrete Element modeling and analysis of shielding effects during the crushing of a grain Wang, P., Bakhtiary, E., Ecker, S., and Arson, C. School of Civil and Environmental Engineering Georgia Institute of Technology, Atlanta, Georgia, USA Christopher, T. School of Mechanical Engineering Georgia Institute of Technology, Atlanta, Georgia, USA Francis, K. School of Electrical Engineering Georgia Institute of Technology, Atlanta, Georgia, USA ABSTRACT: The potential for a particle to crush under one-dimensional compression is critically dependent on the coordination number of that particle. Neighboring particles decrease deviatoric forces at contacts, which reduces tensile stress and subsequent fracture propagation in the crushable particle. This phenomenon is called “shielding effect”. In this paper, we model a sand particle as a spherical cluster of bonded, hexagonally packed, equally sized, non-breakable spheres with the Discrete Element Method (DEM). We use rigid walls to apply forces at the contact with neighboring particles. First, we calibrate the cluster mechanical parameters against published experimental results obtained during unconfined uniaxial compression tests. Then we propose a procedure employed in DEM to generate symmetric and random distributions of walls. We use two loading walls only: the remainder of the walls is used for passive shielding. Force-displacement curves obtained during the crushing simulations clearly show that the peak force reached when the cluster first splits increases with the number of shielding walls, which demonstrates shielding effects. The total resulting compression force applied by the walls increases linearly the coordination number. We expect that our computational method will allow the optimization of crushing in powder technology, and the prevention of crushing in geotechnical engineering.