Field Measurement of Subway-induced Vibration and Application of Hilbert-Huang Transform Method

This paper describes the field measurement results of subway-induced ground vibrations of Line 2 in Shanghai and the application of the HHT method in data analysis procedure. Field measurement was carried out at Shanghai Science Center-Shiji Park interval in order to study the propagation characteristics of the subway-induced vibration. As an adaptive data analysis method,HHT method was adopted to analyze the measurement data. The EEMD method was used, to get the intrinsic mode functions. After performing the Hilbert transform on all the IMF's,the Hilbert spectra presentation was given which would represent precisely the energy distribution of the vibration in the time-frequency plane. The comparison of the Hitbert spectra and wavelet spectra was made. Analysis results show that the vibration data is not strictly stationary. The vibrations are influenced by distance and amplified at certain distance away from the tunnel center. Compared with the wavelet spectrum, the Hilbert spectrum has better time and frequency resolution. High frequency components of vibration fall off faster than the low ones. Field measurement is reliable to study the propagation of the free field ground-borne vibration. The HHT method could be an alternative in the data analysis of subway-induced vibration.