This paper demonstrates results of numerical simulations based on discrete element approach. The triaxial compression behaviour of coarse granular particles that represent railroad ballast is simulated. During laboratory testing, the vertical deformation of ballast layer prepared with two different gradations was assessed under vertical loading. One specimen was simulated using particle size distribution (PSD) recommended by Indraratna and co-workers in the past as an improvement to Australian Standard and the other was prepared with PSD in accordance with Brazilian standard. The discrete element method offers a new resource for accurate investigation of response of railway ballast as evident in controlled laboratory environment as well as field conditions. In this paper, the discrete element method of analysis is used to simulate the geotechnical behaviour of ballast observed during compression testing. The numerical analysis captured the evolution of inter-particle forces as a granular material is subjected to compression test. The article showed a procedure to model ballast testing using DEM, where useful features of the micromechanical analyses such as coordination number, velocity vectors of particles are exhibited.