Field dynamic performance testing and analysis of polyurethane track and ballasted track in a high-speed railway

The dynamic performances of a polyurethane-reinforced ballast bed and an unreinforced ballast bed at an operation site were tested by using the impact excitation technique. The influences of the ballast beds with and without polyurethane reinforcement on the natural frequency were investigated, along with the vertical and longitudinal vibration transmission characteristics of the track structure. The results show the following. Compared to the ballast bed, the polyurethane ballast bed has an inhibitory effect on the rail vibration in the range of 200–400 Hz, but there is an increased rail vibration amplitude in the higher frequency range. The polyurethane-reinforced ballast bed significantly increases the amount and amplitude of the dominant vibration frequencies of the sleeper. As the frequency increases (> 90 Hz), the superstructure of the polyurethane track rapidly transfers from being flexible to rigid, and the track thus absorbs and dissipates the impact load, quickly damping the vibration in the range of 90–470 Hz. The calculation results of the displacement transmission ratio (DTR) proposed in this study also support this finding, suggesting the use of DTR to more intuitively evaluate the vibration damping effect of each component of the track. The polyurethane material reinforces the ballast bed rather than the damping vibration, thereby improving the stability of the track structure.