Improved HHT Algorithm For Blasting Seismic Wave Signal Processing And Its Application

With the rapid development of the national economy,blasting technology has been widely used.While engineering blasting brings convenience to the country's economic construction,the adverse effects of blasting seismic effects on the surrounding environment cannot be ignored.The blasting seismic wave signal has the characteristics of instantaneous,sudden change and shock,which is a typical non-stationary signal.Through signal processing,reliable time,frequency,energy and other characteristic parameters can be extracted from the blasting seismic wave signal,so as to reflect the attenuation law of site blasting vibration.It is of great significance for the control of blasting vibration hazards and the scientific formulation of anti-seismic measures.The current signal processing methods are mostly based on the stationary and linear signal processing methods.These methods have poor processing effect and it is difficult to obtain time-frequency energy parameters reflecting the characteristics of real blasting vibration.Hilbert-Huang Transform(HHT)is an adaptive signal processing method that performs modal decomposition according to the characteristics of the data itself.The characteristics of the monitoring signal itself are well preserved in the analysis process.The results obtained by this method can better reflect the characteristics of the blasting seismic wave monitoring signal itself,and obtain high-resolution time-frequency energy processing results,thereby achieving the purpose of improving the accuracy of non-stationary signal processing.Due to the strong background noise and non-stationary characteristics of blasting seismic wave signal,the traditional HHT has some shortcomings in blasting seismic wave signal processing,such as modal confusion,endpoint effect,and the lack of practical significance of some instantaneous frequencies.The above problems will affect the processing accuracy of traditional HHT blasting seismic wave signal to varying degrees.Based on the National Natural Science Foundation of China " Research on the mechanism of the soft surrounding rock deterioration of slate tunnel under the coordinating effect of the blasting and groundwater(41672260)" and the transverse project,this paper makes a comprehensive analysis on the problems of modal confusion,endpoint effect and the lack of practical significance of some instantaneous frequencies in the traditional HHT algorithm blasting seismic wave signal processing.Combined with the previous research results,the causes of these problems and the adverse effects of these problems on the signal processing accuracy are systematically studied.Finally,the research topic of "Improved HHT Algorithm for Blasting Seismic Wave Signal Processing and its Application" is put forward.On the basis of referring to a large number of domestic and foreign relevant literatures and conducting a large number of field investigations and monitoring,the MATLAB programming language development platform is used to comprehensively analyze the traditional HHT and its improved algorithm.The main research contents and achievements are as follows:1.Research on signal processing method of blasting seismic waveUsing Matlab language programming,the Short Time Fourier Transform(STFT),Continuous Wavelet Transform(CWT),Discrete Wavelet Transform(DWT)and HHT are compared and studied in terms of signal decomposition and reconstruction,signal spectrum analysis,resolution comparison,and noise reduction applications.The adaptability and superiority of HHT in blasting seismic wave signal processing are discussed from many aspects.2.Research on HHT-EMD modal confusion reduction methodThe CEEMD-MPE combined algorithm of Complementary Ensemble Empirical Mode Decomposition(CEEMD)and Multiscale permutation entropy(MPE)is proposed,and combined with the method of solving the maximum value problem in advanced mathematics.The adaptive smoothing noise reduction model of the blasting seismic wave signal is established,which can achieve the purpose of suppressing the inherent modal confusion phenomenon of EMD.3.Research on suppression method of HHT-EMD endpoint effectBased on the development trend of blasting seismic wave signals at the end points and its correlation with global signals,a new method to suppress the endpoint effect of blasting seismic wave signals based on the adaptive matching extension of boundary local feature scales is proposed,and the simulation test is carried out to verify that the proposed method has good suppression effect on the endpoint effect.4.Research on HHT-IMF normalized treatment methodThrough MATLAB programming,EMD mode confusion reduction method and EMD endpoint effect suppression method are combined to form the joint suppression algorithm of EMD mode confusion and endpoint effect.Improved normalized Hilbert transform(INHT)can be obtained by Hilbert transform of frequency modulation component of IMF obtained by EMD mode confusion and endpoint effect joint suppression algorithm.The simulation results show that the INHT algorithm is more stable than the Hilbert transform,and the time-frequency distribution is more accurate and reasonable.5.Research on blasting vibration signal processing method and application based on improved HHT algorithm(1)The application of the adaptive smoothing noise reduction model in the denoising processing of seismic wave signals in highway tunnel expansion blasting shows that the adaptive smoothing noise reduction model can denoise the original signals on the premise of retaining the real components of the original signals,thus suppressing the inherent modal confusion of EMD.It can provide analysis basis for accurate analysis of site blasting vibration attenuation law,provide basis for blasting engineering design and damage control of blasting vibration,and is the premise of scientific formulation of seismic measures.(2)The application of the improved HHT algorithm in the analysis of the blasting network delay of underground caverns.It is found that the actual millisecond time interval obtained by the improved HHT algorithm corresponds to the blasting section designed by the blasting network.By comparing the actual micro-difference time interval with the theoretical delay interval of the detonator,it can be judged whether the detonator is in normal service during construction,which has important practical significance for blasting safety control.(3)The application of the improved HHT algorithm in the time-frequency energy analysis of underwater borehole blasting seismic wave signals shows that the dominant frequency and energy of the signal develop to low frequency with the increase of the detonation distance;The duration of high frequency decreases,the duration of low frequency increases,and the influence range of low frequency increases.The proportion of high frequency energy of blasting seismic wave signals decreases while that of low frequency energy increases.IMF component has different amplifying effect on the particle vibration velocity of the same building under different formations.The resonance effect is the strongest when the natural frequency corresponding to the structure is closest to the dominant frequency of IMF component.It provides a theoretical basis for the control and prediction of underwater borehole blasting vibration hazards.