Simplified methods for wave propagation and soil-structure interaction: The dispersion of layered soil and the approximation of FEBEM results

When working on vibration from traffic, construction or industry, the wave propagation through the soil and the soil-structure interaction is of importance. It is desirable to have the corresponding rules both theoretically founded and practically proved. This contribution wants to show consistent results from exact theory, approximate rules and experiments. At first the dispersion, the frequency-dependent wave-speed of the soil is analysed in detail for layered soil and for soil with continuously increasing stiffness. The wave admittance is calculated as a function of frequency and wave-speed to find out the rules and to get an algorithm that calculates approximately the dispersion of a layered soil. A good correlation is observed between the frequency-dependent wave-speed and the frequency-dependent amplitudes. Therefore, we can use the approximate dispersion in a second procedure which calculates the amplitudes of the dispersal soil. These two algorithms for the dispersion and for the amplitudes - which could be referred to as a "dispersal soil method" - can be used to predict quickly and easily ground vibration due to railway traffic. A similar simplification as for the wave propagation can be found for the track-soil interaction analysis which is demonstrated for a track with ballast mat. A lot of measurements of waves and ground vibration have been performed. Some results are presented here to provide the links between theoretical and experimental methods and to verify the half-space theory for real soil.