A track model for railway-induced ground vibration resulting from a transition zone

Accurate computational models are required to predict the ground-borne vibration caused by railway traffic. Since these models generally require substantial computational effort, much research is focused on developing computationally efficient methods by either exploiting the regularity of the problem geometry in the direction along the track or by assuming a simplified track structure. This paper presents a track modeling approach based on a wave analysis technique for multi-coupled periodic structures. The track and part of the soil are modeled with finite elements, while a perfectly matched layer absorbs waves that travel in the semi-infinite soil. A case study that investigates a track with a transition zone between the ballasted and the slab track is presented. The track model is verified by comparing it with a periodic track model by using the Floquet transform. The train-track interaction force and the free field vibration are computed for transition zones with gradual and sudden increase in stiffness, respectively. It is found that, at higher train speeds, it is more important to have a more gradual increase in stiffness in the transition zone.