A numerical study on the stress changes in the ballast due to train passages

Abstract

At railway bridge approaches the track stiffness may vary rapidly and often differen- tial settlements take place between the stiff structure and the approach section of the track. These differential settlements lead to uneven track profiles and the appearance of voids between the base of the sleepers and the ballast on the approach segment. The ballast and the sub-ballast are the unbound granular materials that carry the track, have a non-linear stress dependent behaviour, and degrade many times faster at transitions. The present study focuses on the implementation of these non-linear aspects in a finite element algorithm for the dynamic simulation of a railway transition. Linear and nonlinear constitutive laws of the unbound aggregates that comprise the trackbed, and straight and uneven track profiles with hanging sleepers, are used to reproduce the behaviour of a railway bridge approach. Stress and deformation results are pre- sented and discussed for both linear and non-linear scenarios. The results show that the consideration of these non-linear aspects is relevant for the modelling of railway transitions.