Abstract:

When using empirical mode decomposition(EMD) to process blasting vibration signal, the problem of mode aliasing occurs. Hence, the ensemble empirical mode decomposition(EEMD) method is introduced to denoise the blasting vibration signal; and the characteristic information of blasting vibration signals in urban tunnel excavation is analyzed to study the vibration effect of urban tunnel blasting excavation. By taking the blasting excavation project of Urumqi Rail Transit Line 1 for example, the original blasting vibration signals are denoised by EEMD and EMD methods; the singlenoise ratio(SNR) method and the rootmeansquare error(RMSE) method are used to quantitatively evaluate and compare the results to gain a more accurate signal denoising method; and the timefrequency and energy distribution characteristics of the denoised blasting vibration signal are analyzed by Hilbert transform. The study results show that: (1) The SNR value and RMSE value of denosing result by EEMD method are 30.51 and 0.005 5, respectively, and those of denosing result by EMD are 20.88 and 0.010, respectively, which show that the denosing effect of EEMD method is better than that of EMD method. (2) In current blasting operation, the energy of blasting vibration is mainly distributed in frequency section of 5-80 Hz, mainly in frequency section below 50 Hz; hence, proper measures should be taken to control the impact of blasting vibration on buildings or structures. (3) The instantaneous energy peak value of blasting vibration coincides with the peak value of vibration velocity, which indicates that the instantaneous energy spectrum can better reflect the variation law of vibration effect with time in blasting process. (4) Based on the research conclusion of signal denoising and analysis, the blasting vibration control technology of metro tunnel is put forward.

Key words: ensemble empirical mode decomposition(EEMD) method, signal denosing, blasting vibration, signal analysis, metro tunnel