Numerical simulation of track settlements based on an iterative holistic approach

A track settlement algorithm implemented in a multibody simulation software (MBS) is presented. The purpose is to extend the capabilities of a railway track model so a ballast degradation analysis can be performed. The main idea is to implement a methodology that enables a simulation of the train/track interaction and its influence on the overall track settlement mechanism of a regular track section.

For this purpose, the common moving track model widely used in MBS codes is changed to a model in which the track stands still. This is done by inserting, in a discrete way, a set of mass-spring-damper systems along the track. The new way in which the track is modelled allows us, in a more accurate way, to take into account different capabilities of the track model, such as track flexibility and damping conditions, discrete support conditions given by the sleeper distance, and the possibility of modelling each track component independently along the track section.

In the novel methodology presented in this work, a settlement algorithm has been directly implemented in the MBS package. The latter makes it possible to simulate the track degradation process given by the settlement of the ballast layer. The process consists of two main phases. In the first one, the train/track interaction analysis is carried out.

In the second one, the dynamic forces are obtained at the supports along the track, which are then taken and transformed, by applying a settlement law, into vertical displacements that in turn are applied as longitudinal level irregularities in the wheel/rail contact. The process is completed by linking the aforementioned phases in a cyclic mode, considering as many iterations as desired.

This work presents an efficient and novel technique that makes MBS code capable of predicting the impact of the accumulated track settlement on the train/track interaction.