Suiker A.S.J., Metrikine A.V. and de Borst R.


Dynamic behavior of a layer of discrete particles - Part 1 Analysis of body waves and eigen modes


Journal of Sound and Vibration 240(1), 1-18, 2001



Summary. The current paper is one in a series of two, and discusses the body wave propagation and the eigen modes for a layer of discrete particles. This configuration is representative for a ballast layer used in ordinary railway tracks. The discrete nature of the ballast is simulated via an elastic 9-cell square lattice. After deriving the equations of motion for the lattice, the long-wave approximation for the equations of motion is compared with the equations of motion for a classic elastic continuum. This comparison yields relations between the macroscopic continuum parameters and the microscopic lattice parameters. Next, the dispersion curves that characterize the eigen modes of the discrete layer are derived. The difference between these dispersion curves and those of a continuous layer are elucidated. Through a parametric study, the influence is shown of the particle diameter and of the layer thickness on the dynamic response. In an accompanying paper, the layer response to a moving, harmonically vibrating load is analyzed, which is representative for a ballast track that is subjected to an instantaneous train axle passage.