High speed railway tracks suffer from a differential settlement and material degradation near the bridges. This phenomena causes more maintenance of the track and safety issues. In this project we would like to simulate the track sub-structure to investigate the mechanism of this issue, and provide mitigation solutions. Discrete element method was chosen to simulate the granular material under the rail structure. This method models each particle as a rigid object with contact stiffness. Throughout the simulation, force and displacement equations are solved for each single particle in the model at each calculation time-step. The time-step of the calculation depends on the size and mass of the materials. Since there are very fine material in the simulation (less than 1 mm), the calculation time-step is so small (in the order of 1e-8 seconds). The model is also quite large so that it can include the long railway and the bridge with different underneath layers. As a result, there would be millions of particles to be solved for millions of steps. The computational power of normal PCs is incapable of solving this problem. Therefore, we require much faster computers to run our simulations.