Steinhauser P.

Noise and vibrations are considered to be the most disturbing environmental problems of railways. While prediction and abatement of noise are well established techniques, vibrations are more complicated to handle. Reasons are the complex transmission behavior of the underground and the feedback by the dynamic properties of buildings, which control the frequency transfer functions and the level of vibration experienced by local residents. Therefore reliable vibration forecasts are necessary, especially for shallow sections of new railway tunnels in residential areas. Due to the extremely limited knowledge of underground structures vibration experiments are indispensable to determine frequency transfer functions for the entire transmission path. Refraction seismic profiles for P- and S-waves enable the calculation of eigenfrequency models from the underground before starting construction. As soon as the basic tunnel construction is completed a heavy seismic servo hydraulic vibrator can generate the frequency sweeps covering the entire spectrum of railway vibrations. This so-called VibroScan method delivers frequency transfer functions for the entire transmission path to local residents. It is shown that reliable forecasts are obtained when the dynamic parameters of the vibrator match those of trains. Thus the design parameters of resilient elements like floating slabs can be calculated. Usually insertion loss calculations are carried out for resilient elements placed on a rigid base, but taking advantage of the seismic cross sections it is possible to determine the influence of the real, soft layered substratum on the insertion loss as well.