Abstract
The track deterioration rate is strongly influenced by the ballast behaviour under commercial traffic. In order to restore the initial track geometry, different maintenance processes are performed, like tamping, dynamic stabilisation. A better understanding of the ballast behaviour under these operations on a portion of railway track is a key to optimize the process, to limit degradation and to propose some concept for a better homogeneous compaction. The numerical simulation is developed here to investigate the mechanical behaviour of ballast. However, the main difficulties of this research action concerns the size of the granular system simulation increasing both in term of number of grains and of process duration. The purpose of this thesis is to develop an efficient numerical tool allows to realize faster computations devoted to large-scale granular samples. In this framework, the Non-Smooth Contact Dynamics (NSCD) of three-dimensional Discrete Element Method (DEM) simulations, improved by Domain Decomposition Method (DDM) and processed with the Shared Memory parallel technique (using OpenMP) has been applied to study the ballast media mechanics.