Transition zones corresponding to the passage from railway tracks on embankment to natural ground or settlement free structures are frequently problematic for maintenance. Changing stiffness of the track and differential settlements are the main causes for the degradation of tracks and foundations at transitions. This paper presents a methodology to predict the settlement of the track due to train loading, applicable to transition zones. The methodology is based on dynamic calculations using a (non-linear) train–track interaction model and an incremental settlement model. Important non-linear aspects in dynamic models for railway transitions are the loss of contact between the sleepers and the ballast and the non-linear constitutive behaviour of the ballast. The settlements are calculated paying attention to the factors that most influence the long-term behaviour of ballast, such as the amplitude of the applied dynamic force and the number of loading cycles. The importance of the dynamic loading from the trains and of the constitutive models used for the trackbed layers is analysed.

Abrupt track vertical stiffness variations along railway tracks can lead to increased dynamic loads, asymmetric deformations, damaged track components, and consequently, increased maintenance costs. The junction of slab track and ballasted track is one of the existing areas where vertical track stiffness can suddenly change, therefore requiring a transition zone that smoothes the track stiffness change. One of the methods for constructing the transition zone at the junction of slab and ballasted tracks is to install auxiliary rails along the transition zone. In the present study, the dynamic behavior of this type of transition zone was evaluated by a train-track interaction model. For this purpose, a 3D model of the railway track was made, representing the slab track, the transition zone, and the ballasted track. Then, the modeling results were validated by the results of field tests. Afterwards, in order to study the dynamic behavior of the transition zone with auxiliary rails, different sensitive analyses, such as vehicle speed, vehicle load, number of auxiliary rails and railpad stiffness, were performed with the model. The obtained results showed that the use of auxiliary rails reduced the rail deflection variations along the transition zone from 35% to 28% for low and medium speeds (120, 160, 200 km/h), and from 40% to 33% for high speeds (250, 300 km/h).