Towards high-speed railway - effects on nearby structures and estimation of ballast degradation

Abstract

Passing trains cause vibrations and load cycles in the ballast, subsoil, and structures. These cycles degrade ballast over time. Indraratna et al. (2010) and Sun et al. (2014) have shown that the higher speed of the train does not necessarily increase the load much, but the higher frequencies of vibrations lead to quicker ballast degradation. This work investigated the effects of vibrations induced by high-speed trains with varying ballast degradation levels on nearby structures based on the research conducted with the FEM model. The thesis also proposed a method for initially estimating the relationship between increasing train speeds and track maintenance intervals according to a simple model Sun et al. (2014) developed for estimating the degree of ballast degradation based on train speeds and load cycles.

In total, the work shows 48 Finite Element Method simulations. Combing 6 signals of train displacement, 4 cross-sections, and considering 3 different ballast conditions for three of these signals. The findings indicate that increasing the train speed has a significant impact on the vibration of nearby structures. If the train speed is raised from 120km/h to 200km/h, the vibration of the structures, excluding the sheet pile wall, will increase by around 20% to 40%. However, the vibration of the sheet pile wall will be amplified by two times. The impact of ballast conditions on vibrations is only noteworthy when its condition is poor.

Additionally, a resonance effect was found in the numerical calculations when the train speed was increased to 160km/h, which suggests that resonance may occur in a certain section of the Kokemäki -Pori railway line.