Discrete elements method to model ballast behaviour under railway turnouts

Ballast behaviour has a profound impact on global track performance and durability, particularly for turnouts where dynamic forces are substantial. As ballast is a discontinuous material, this paper proposes the application of a Discrete Element Method (DEM) to model its behaviour under a conventional track turnout, a new approach that has not yet been tried for turnouts, only for main tracks. The model was validated with real vertical stiffness data measured in an actual turnout and used to analyse ballast behaviour under dynamic traffic loads. The results show remarkable differences in ballast behaviour for train speeds close to 180 km/h, as particle interactions and stress levels extend to the entire ballast layer. At lower speeds, the stress under the sleeper forms a trapezoidal shape for a given cross-section, while the rest of the layer remains barely affected. Overall, the DEM model is a reliable tool for simulating ballast behaviour and provides new insights into ballast-turnout interactions, which may help improve maintenance in these essential track elements.