Influence of Frequency-Dependent Dynamic Parameters of Rail Pads on Environmental Vibration Induced by Subways in a Tunnel

On the basis of verification of a new frequency-domain method with measured data, the influence of frequency-dependent dynamic parameters of rail pads on environmental vibration is investigated. The contrast between theoretical and measured data shows that the new approach is reasonable and provides high accuracy. The influence of frequency-dependent stiffness of rail pads on environmental vibration can be neglected below the one-third octave frequency of 25 Hz and yet alters not only the frequency-domain amplitudes of environmental vibration but also its frequency distribution above 25 Hz. The frequency-dependent damping of rail pads slightly increases the maximum ground vibration level in one-third octave frequencies and yet reduces that of an above-the-center frequency with the maximum vibration level. Simply increasing the constant stiffness of rail pads or decreasing the constant damping can give the smallest error in the predicted ground vibration in either the low-frequency or the high-frequency domain. With continuous deterioration of track irregularity, regardless of frequency-dependent dynamic parameters of rail pads, the constant stiffness or damping of rail pads with the smallest error is not invariable.