## 2 Measurement Campaign for the Bridge, Tunnel and Surface Lines
The irregularities stem from track alignment errors at low and mid frequencies, from wheel out-of-roundness at mid and high frequencies and from long wavelength rail roughness at high frequencies, see [34]. The track vibrations are presented as one-third octave band spectra of the velocities of the rail measurement points in Figure 7. The velocity spectra are almost constant with frequency and generally increasing with the train speed. The amplitudes are between 0.3 mm/s for 63 km/h and 3 mm/s for 160 km/h. A characteristic speed-dependent maximum for three one-third octaves can be found, which is from 12 to 20 Hz for 160 km/h. This maximum is due to the impulse from the passage of the static train loads. The related minima (for example at 10 and 25 Hz for 160 km/h) are an effect of the axle sequence in a bogie [3]. Whereas the low frequencies stem from the passage of the static axle loads, the high frequencies are generated by the dynamic axle loads. The tunnel line shows specific amplitudes and dynamic loads around the vehicle-track resonance at 63 Hz. The bridge track has the highest and nearly constant amplitudes at high frequencies whereas the ballast track on the soil surface has the lowest high-frequency level. The sleeper vibrations on the tunnel line (Figure 7b) are only one tenth of the rail amplitudes (Figure 7a). On the bridge and especially on the surface line, the difference between the rail and sleeper amplitudes is smaller due to the stiffer rail pads used for the ballast track. The track slab in the tunnel (Figure 7c) shows similar spectra as the sleepers. All track measurement points in the tunnel have a clear reduction in the frequency range between the speed-dependent axle impulse maximum at 6 to 16 Hz and the vehicle-track resonance at 63 Hz. The vibration amplitudes of the bridge (Figure 7f) are clearly smaller than the rail and the sleeper amplitudes. Peaks at the 6 and 10 Hz one-third octave indicate bridge resonances which are prominent for the 100 km/h and, especially, 160 km/h train speeds, where the amplitudes of 2 mm/s are even higher than the sleeper amplitudes. It is expected that the bridge resonances could also be seen in the ground vibration as has been calculated in [1]. The ground vibrations measured above the tunnel line are presented as one-third octave spectra in Figure 8. As with the amplitudes in Figure 5b, the frequency characteristics of the different measurement points are very similar, and the spectra are only somewhat smaller for the farthest distances. The mid-frequency maxima can be found for 125 and 160 km/h whereas the more dominant high-frequency maximum around 63 Hz is present for all train speeds. The frequency range of this maximum is wider than for the vehicle and the track and includes frequencies from 32 to 80 Hz. The ground-vibration spectra at the surface line vary strongly with the distance from the track. The spectra close to the track (Figure 7i) are almost constant and include the quasi-static component below 8 Hz, at least for the highest train speeds. At 5 m distance (Figure 9a) the quasi-static component has already disappeared and the high-frequency part of the spectrum is dominant. This changes with increasing distance. The high-frequency part from 40 to 80 Hz and the mid-frequency part around 12 Hz are equally important at 17.5 m (Figure 9b) whereas the latter is already dominant at 30 m (Figure 9c). Finally at 100 m, only the peak at 12 Hz is left over (Figure 9d). These characteristics are due to the wave transfer properties of the soil where the material damping reduces the high-frequency content considerably. Figure 7: One-third octave band spectra of the rail (**a**,**d**,**g**), the sleeper (**b**,**e**,**h**) and environmental (**c**,**f**,**i**) velocities, (**a**–**c**) tunnel, (**d**–**f**) bridge and (**g**–**i**) surface line, track slab (**c**), one-third point of the bridge deck (f), near field of the surface track (2.5 m), (**i**), for different train speeds: \(\square\) 160, \(\circ\) 125, \(\triangle\) 100, + 80, \(\times\) 63 km/h.