On the Influence of Iterative Model Updating on Long-Term Differential Settlement in Ballasted Railway Tracks

Paper in proceeding, 2026

Predicting differential track settlement and degradation of vertical track geometry (longitudinal level) remains a significant challenge for railway maintenance planning, particularly on lines with variable support conditions. This study compares two strategies for long-term settlement prediction in open ballasted railway tracks: a non-iterative approach based on a constant load spectrum, and an iterative approach in which the track model is updated as settlement evolves. Dynamic vehicle--track interaction analyses are performed using two independent numerical frameworks, from which maximum sleeper--ballast contact forces for each sleeper are obtained and used as input to empirical settlement models. The non-iterative approach assumes a fixed load distribution throughout the analysis, whereas the iterative approach captures the evolving track geometry and the associated redistribution of loads. The results show that both approaches yield similar overall settlement trends and spatial patterns. However, the iterative approach provides additional insight into load redistribution and the influence of evolving support conditions, which are important for assessing localised track behaviour. The comparison highlights when simplified non-iterative modelling is sufficient, as well as the added value of iterative analysis for representing long-term track behaviour.