High-speed train induced vibrations

Abstract

Nowadays trains operating at high speeds can cause strong vibrations especially if they cross soft soils. These oscillations influence the track on which the train is running and can impair its structure. Besides that vibrations propagate to the environment where they may have detrimental affects. The aim of this study is to introduce the characteristics of these high-speed trains induced vibrations and possibilities to lower them. The first part of the thesis illustrates the generation and propagation of vibrations caused by high-speed trains. Primarily the physical nature of dynamic behaviour is explained. Dynamic load characteristics are exposed to clarify the effects a passing train has on the underlying track and subgrade. Sources of dynamic excitation induced by high-speed trains are specified and it is shown are specified and it is shown that the generation is mainly dependent on train and track characteristics as well as on features of the underlying and adjacent ground. Afterwards the propagation of vibrations is considered and main characteristics of seismic waves such as Compressive-, Shear- and Rayleigh-waves are shown. Further their propagation properties and attenuation features due to geometrical damping are depicted and it is realised that Rayleigh- waves are the dominant among the seismic waves regarding the effects on tracks and the environment. Additionally amplification of wave amplitudes evoked by critical speeds and its consequences are regarded and influence of different track structures as well as several soil-types on vibrations is described. The effects of vibrations on several receivers are discussed in the second part. The influence on the environment is one of the most important consequences of propagating waves. Concerned are mainly building structures and sensitive equipment that can be damaged by vibrations as well as human beings who might be annoyed by vibrating buildings. Another effect vibrations can have is damaging the railway structure itself what can have detrimental impact on the driving safety and maintenance costs. Further diverse vibration prediction methods are viewed, which should be undertaken in case of improving existing lines or increasing train speeds. Also if new railway-lines or buildings along tracks are planned vibration prediction must be attempted. The work gives an overview on empirical methods based on experiences gained in recent years. Besides those, field measurements including methods to determine shear wave velocities, vibration amplitudes and -velocities are described as well as laboratory test and computational models. Thereafter actually existing regulations and standards concerning vibrations are described and valued. The study is mainly focused on Internal Standards as well as national regulations and standards of Scandinavian countries and discusses in which topics there is still a lack of rules. Lastly vibration control measures are considered. Here measures executed at different locations are described. The study comprises measures undertaken at the vibration sources, i.e. at vehicles, track structures and -foundations, at the propagation path, such as ground improvements and vibration isolation, and measures at vibration receivers that means at building and their foundations. /Kir10