Effect of passing metro trains on uncertainty of vibration source intensity: monitoring tests

The source intensity of metro-induced vibrations is defined as the vertical weighted vibration acceleration level on a tunnel wall. It is traditionally determined using the empirical method or analogical test. However, recent research has indicated that tunnel vibration responses vary significantly according to the passing train, likely owing to the influence of wheels worn out-of-round. To analyse the associated uncertainty of the vibration source intensity, five monitoring tests were performed in a metro tunnel over the course of one year. Each test lasted 24 h, during which the vibration responses of all the passing trains were recorded. Then, information describing the operating mileage for all passing trains was collected to quantitatively analyse the relationship between the vibration source intensity and the wheel conditions. The results indicate that different trains can generate source intensities with significant differences greater than 10 dB in most 1/3 octave bands between 40 and 315 Hz. The tunnel vibration responses increased with the net operating mileage of the passing trains, and the vibrations between 40 and 315 Hz decreased by more than 20 dB after wheel re-profiling. The maximum and average values of the tunnel vibration responses decreased by 8 and 5 dB, respectively, after rail grinding.

Automated summary

The intensity of metro-induced vibrations in tunnels is influenced by the condition of train wheels, causing significant differences in vibration intensity between passing trains. Vibration responses in tunnels increase with the operating mileage of passing trains, but decrease after wheel re-profiling.