Abstract
In the North West of France, more particularly in the region of the Somme Bay, where the ground is constituted mainly of peat, observation of the surface of the soil near railway tracks has revealed high levels of displacement. This paper, contains a prediction model and diagnosis of vibration near the track. A model of a railway track on layered ground subjected to a moving train has been built and the calculation method uses Fourier transform formalism for a semi-analytical solution in the wave number domain. It includes all elements of the track and allows a parametric analysis of its different elements and evaluation of vertical displacement according to the speed, weight and composition of each train. The diagnosis has been performed with in situ measurements and with the aim of the validation of the model. A parameter study of the ground undertaken by seismic measurements shows a critical speed close to 100 m/s while the studied trains are moving with sub-Rayleigh speeds. Measurements give us a lot of information about lateral and vertical acceleration on the soil's surface and parts of the track. For high speeds and freight trains, displacement reaches more than 10 mm.
Highlights
Wðb; tÞ Z w*ðbÞeiU0t; Fðb; tÞ Z F* ðbÞeiU0t where c is the speed of the train, U0 is the excitation frequency, * indicates that we study the steady state solution and b and g are the wave numbers relative to x and y
The first part of this paper, is concerned with numerical simulation tools suited to the problem of the propagation of vibration from railway traffic and taking into account the various elements of the structure
The numerical model is proposed to ensure the interaction between track and ground and possible simplifications for the ground with, the restriction of a linear hypothesis for the behavior of all materials
Summary
The consequences of railway traffic, in terms of environmental damage (vibration, noise and various polluters) are all the more important in view of the fact that the speed of trains has increased. This increase in speed is sought after for railway trains like the high speed T.G.V. in France. For relatively soft ground (clay, peat, .), a Rayleigh wave speed of less than 100 m/s is possible, and in this case the super-Rayleigh regime is reached for trains moving at high speed. This situation induces high levels of displacement in the rail and at the ground’s surface, which has no impact on the comfort of passengers, but is worrying for the wear and tear of the tracks and neighbouring structures
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