ENERGY ANALYSIS OF GROUND VIBRATION INDUCED BY SUBWAY TRAINS

In-situ vibration measuring was carried out for the ground-borne vibration induced by subway trains in Shanghai. Based on the acceleration recordings, firstly, the characteristics of energy distribution in time domain and frequency domain are obtained respectively by the traditional methods. Accordingly, the attenuation curve is analyzed and the dominant frequency range is obtained. Secondly, the time-frequency energy spectrum and accumulated energy curve are presented by continuous wavelet transform based on Mexican hat wavelet. The train formation is the direct reason to the non-stationary ground vibration. To most of the measuring sites, the scope of the impact of the trains on the vibration is limited mainly by the length of two cars. But in the enlarged area of vibrational energy, the scope of the impact of the trains is limited basically by the length of the car passing by.