A reduced scale experiment of three sleepers is presented in order to better understand the dynamic behavior of railway tracks, to identify the evolution of the mechanical properties of the tracks and the settlement of sleepers versus the number of cycles. This experiment is characterized by three important points: (1) A natural soil is used to simulate the platform. (2) Three sleepers are used to simulate moving loads due to passing trains at high speeds. (3) With this experiment, the structure is submitted into high speeds reaching 400 kmh-1. Due to experimental results offered by this experiment, soil behavior is identified. It is clear that the behavior of soil in statics as well as in dynamics is non linear. Hence, its equivalent modulus of elasticity depends on the associated force. Using the measured pressures in soil obtained during experiments at different rolling speeds and considering that soil represents an infinite half-space, a mean equivalent elasticity modulus is determined. Damping ratio of soil is also identified with respect to a sinusoidal loading at 10 Hz. Concerning the behavior of the complete structure (soil, ballast and sleepers), it is noticed that stiffnesses (dynamic and static) are very variable in terms of the number of cycles. One can find a maximum static stiffness 88 percent larger than the initial one (at the beginning of the experiment), and a maximum dynamic stiffness 67 percent larger than the initial one. The dynamic effect can be noted by comparing the two static and dynamic stiffnesses where one can find a difference of 40 percent. Concerning the settlement increment, it was observed that its value depends strongly on the velocity of the load. An important parameter to estimate its value is the acceleration of sleepers or in ballast. Critical values are found between 1.4 and 2g depending if the accelerations of sleepers or in ballast is measured and depending also on the direction of measurement. Above these critical values the settlement is much stronger. A large scattering in the values of the mechanical parameters such as the elastic displacement, the acceleration or the settlement for large accelerations is also observed.
Experimental settlement and dynamic behavior of a portion of ballasted railway track under high speed trains
Versuchssenkung und dynamisches Verhalten eines Abschnittes eines beschotterten Eisenbahngleises unter Hochgeschwindigkeitszügen
Journal of Sound and Vibration ; 316 , 1-5 ; 211-233
2008
23 Seiten, 25 Bilder, 5 Tabellen, 18 Quellen
Article (Journal)
English
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