# Blasting Vibration Control and Signal Analysis of Adjacent Existing Deterioration Tunnels
## 5 Wavelet Packet Analysis of Measured Data  
The natural vibration frequency of the existing tunnel is generally low, and the main frequency of blasting vibration is also low. If the two frequencies are the same or similar, a resonance phenomenon will occur. The resonance phenomenon is unfavorable to the deterioration of the tunnel. We need to clarify the main frequency distribution of the measured data to avoid this phenomenon. Blasting seismic waves are a kind of complex, non-stationary random signal with the characteristics of short time and sudden change. At present, time-frequency analysis methods have been widely used in the analysis of blasting vibration signals, mainly including fast Fourier transform, HHT analysis, and wavelet packet analysis methods. Among them, the fast Fourier transform has serious shortcomings in time-frequency analysis. The analysis accuracy of HHT analysis in the signal boundary region is poor, and the \"flying wing\" phenomenon often appears at the end [22]. Wavelet packet analysis has good adaptability and high resolution and has obvious advantages in the analysis of blasting vibration signals. In the field blasting scheme, mechanical cutting combined with ordinary detonator blasting is used. The blasting vibration signal under this method is analyzed by wavelet packet, and the relationship between vibration velocity energy and frequency is deeply studied. Wavelet packet energy analysis can reflect the excitation effect of blasting vibration on building structure from intensity and frequency. The main excitation frequency interval of the dynamic response of the building structure is determined by signal decomposition and reconstruction. Thus, the stability of existing deterioration tunnels can be further guaranteed. [PERSON] [23] and [PERSON] et al. [24] used wavelet packet energy spectrum analysis to analyze the distribution of blasting vibration signals in the frequency band. [PERSON] [25] studied vibration caused by blasting seismic waves based on wavelet transform and wavelet analysis techniques. [PERSON] [26] used the wavelet packet analysis method to compare the vibration characteristics in the near and far regions of deep-hole step blasting and discussed the energy frequency band distribution law in the near and far region. Based on the wavelet packet energy analysis method, the distribution of blasting vibration signal energy in each frequency band is discussed, which provides a way to evaluate the safety of blasting vibration and reduce the damage of blasting vibration. Daubechies wavelet basis function has good compact support, smoothness, continuity, and symmetry. It is widely used in the analysis and research of engineering signals [27]. In this paper, MATLAB is used to decompose and reconstruct the measured signals of the measuring points 1 and 2 with a 7-layer wavelet packet of db8 wavelet base [28], and the reconstructed nodes are analyzed in the spectrum and studied in energy distribution. Figure 14: Change of peak vibration velocity. (The red numbers represent the rate of change). The instrument sampling frequency is 4000 Hz, and the Nyquist frequency is 2000 Hz. There are total of 7 layers of vibration signal decomposition and 128 nodes, with each node corresponding to a sub-frequency. Therefore, the obtained bandwidth of each frequency band is 15.625 Hz, and the lowest frequency band is 0-15.625 Hz. After decomposition, the frequency band distribution range of each layer signal is shown in Table 6. In the table, Si,j represent the coefficients decomposed to the JTH wavelet packet in the ith layer; i = 1, 2, 3,..., n; j = 0,..., 2, \(i-1\). Wavelet packet analysis is used to reflect the excitation effect of blasting vibration on the deterioration tunnel from two aspects: intensity and frequency. The main excitation frequency interval of the dynamic response of the deterioration tunnel is determined by decomposition and reconstruction.