Investigating of TDA Effect on Reduction of Train Induced Vibrations

Field studies in many countries like USA and South Korea confirms the acceptable performance of TDA material as sub-ballast layer on reducing the train induced vibrations. However, comparing the achieved results in the mentioned studies shows some differences in the exact range of TDA performance frequency in vibration reduction. So in this study, dynamic behaviour of ballasted track with and without TDA as sub-ballast layer was evaluated with using impulse-response (IR) test equipment’s. For this purpose a prototype of ballasted track with and without TDA layer was established and many IR tests were carried out. The impact was imposed on the track by using a 93.5 kg falling hammer and the vertical particle velocity were monitored in the points located in the vicinity of the track by using Geophone. Depending on the position of impact, results were shown in three different kinds of velocity-time, velocity-distance and velocity-frequency curves. Processing the obtained results reveals the TDA efficiency in vibration reduction in the range of 0-500 Hz. The reduction magnitude varies between 17 to 46 dB when the impact imposed on ballast while it varies in the range of 6 to 32 and 6 to 47 when impact location were on sleeper and rail, respectively. As a result of this experimental study, TDA with particle size of 5 to 50 mm with 20 cm thickness creates 6 to 47 dB reduction in vibrations with frequency range of 32 to 250 Hz.