Site-Specific Amplitude-Distance Laws, Wave Velocities, Damping, and Transfer Functions of the Soil from Hammer Impacts and Application to Railway-Induced Ground Vibration: Similarities and Mid-Frequency Differences

Abstract

PurposeThe purpose of this article is to check if and how hammer experiments can be applied to the prediction of railway vibration.MethodsThe propagation of ground vibrations is theoretically analysed with frequency-wavenumber and simplified methods. Experimental methods are presented which can characterise the site-specific ground vibrations by wave velocities, stiffness and damping. Measurements with hammer and train excitation have been performed at several sites.Results The one-third octave spectra show the stiffness-dependent amplitudes and the low- and high-frequency filter effects due to the layering and the damping of the soil. Specific train effects, an additional high-frequency filter, the sleeper passage frequency, and an amplified mid-frequency component can be clearly found. The attenuation with distance is analysed in detail where the theoretical exponential and the empirical frequency-dependent power law are considered. Hammer and train excitation show the same site-specific effects which are mainly due to the stronger or weaker damping of the soil. The train attenuation is generally weaker than the hammer attenuation. The attenuation exponent of the power law, which is strongly dependent on the site and the frequency, is reduced for the train vibration by 0.3–0.5 in agreement with the theory. Reasons are discussed for the overall power law and for the dominating mid-frequency component.ConclusionTherefore, it can be concluded that hammer experiments can well be used for the prediction of train vibrations.