Comparison and analysis of vibration characteristics of different subway tracks

To study the damping effect of different track structures on the environmental vibration, field tests of train-induced vertical acceleration were performed on four types of track structures, namely, ordinary track (OT), medium vibration-damping fastener track (MVDFT), floating-ladder track (FLT) and steel-spring floating slab track (SSFST). The measurement points were set on the rails, track slabs, and tunnel walls. Eventually, the time domain, frequency domain, and one-third- octave frequency division vibration level were adopted to investigate the vibration characteristics of four track structures. The results were obtained as follows. (1) The root-mean-square acceleration values of the four track structures at different measurement points were analyzed in the time domain. Overall, the results could not effectively reflect the damping capacity of the vibration-reduction measures. (2) Based on the one-third octave frequency analysis, regarding 10À6 m/s2 as the decibel reference value, we found that three vibration-reduction measures' vertical vibration level of the tunnel wall was significantly lower than that of OT. Specifically, the damping effect of SSFST was the most obvious. The Z-weighted vibration levels of the three vibration-reduction measures on the tunnel wall have been reduced by 8.919, 11.745 and 13.744 dB, respectively. (3) According to the results of the vibration-transmission characteristics in the frequency domain, the main vibration-frequency regions of the four track structures at the track slab and tunnel wall were all in the range of 1 to 20,00 Hz. Concerning OT, MVDFT, FLT, and SSFST, the peak values of the vibration transmission from the rail to the tunnel wall sequentially decreased, and the damping effect sequentially increased. This paper compared the damping capacity of the above four track structures at 1 to 80 Hz according to ISO 2631-1. In addition, their more detailed vibration characteristics at 1 to 2000 Hz were also considered. It aims to provide a more comprehensive study for the application of subway vibration-reduction measures.