Ground vibration generated by a harmonic load acting on a railway track

A calculation method has been produced for the propagation of vibration in the ground from a stationary oscillating load applied via a railway track structure. The model includes the track as an infinite layered beam structure resting on a ground made up of infinite parallel homogeneous elastic layers. These layers may either be constrained at the lower interface or coupled to an elastic half-space. A similar model, based on wave propagating finite elements, has previously been shown to be useful in predicting the behaviour of real soils and railway tracks, but the applicability of that model was limited by long computation times. The present method is more efficient in calculating the responses at a large number of positions. The development of the theory allows analysis in terms of the amplitudes of different wave types propagating along, and normal to, the track. Example calculations are presented for a ground consisting of a layer on a half-space. By changing only the depth of the layer, two different wave propagation regimes are found, the first where propagation takes place via modes of the layer and the second, where propagation takes place via the bulk waves in the layer and the Rayleigh wave in the substratum. Both examples show the track structure to have a strong effect on the directivity and amplitude of the response of the ground surface. (C) 1999 Academic Press.