Research On Resonance Frequency Shift Mechanism Of Blasting Vibration Based On Doppler Effect

Blasting vibration ranks first among the four harmful effects of blasting.The propagation of blasting seismic wave and resulting rock mass vibration are very complicated processes,and the amplitude and frequency of blasting vibration vary with time and space.Correlationa l research shows that the damage caused by blasting vibration is related to particle peak vibration velocity(PPV).The damage caused by blasting vibration is not only related to PPV,but also related to parameter such as frequency.Considering the research results and practical experience at home and abroad,the national standard Safety Regulations for Blasting(GB6722-2014)takes the PPV and the dominant frequency of vibration as the joint criterion of blasting vibration safety.With the development of blasting vibration control,more and more attention has been paid to the research of blasting vibration frequency.The frequency spectrum analysis of blasting vibration is the foundation of blasting vibration control.MATLAB is used to analyze the frequency spectrum of blasting vibration data.The forced vibration of rock mass under millisecond delay blasting and the Doppler Effect during the propagation of blasting seismic wave are demonstrated by calculation and analysis of numerical simulation and field test.The forced vibration response of rock mass under the action of delayed blasting of the same section of detonator is analyzed,and the resonance frequency of rock mass under the action of delayed blasting of the same section of detonator is accurately identified by means of modal identification method,and the resonance frequency deviation caused by doppler effect is studied by numerical simulation method.On this basis,the vibration frequency generated by millisecond delay initiation is used as the control base frequency,and the frequency offset generated by Doppler Effect is used to obtain the "frequency el ipse" which can precisely quantify the frequency around the detonation source.Finally,the obtained rules are verified by the blasting test on the excavation site of the dam foundation of Baihetan hydropower station.The following conclusions are obtained through analysis and calculation:(1)Under the action of delayed blasting of the same section of detonator,the mult ireference point complex exponential method is used to process the data on both sides of the detonation zone,and the obtained blasting vibration frequency is two groups of resonant frequencies,indicating that the vibration of rock mass is forced vibration.It is also shown that the resonant frequency can be obtained by processing the blasting vibration data with the method of modal identification.(2)In the process of interval delay blasting,due to the relative motion between the blasting source and the measuring point,the blasting seismic wave has Doppler Effect in the propagation process.Due to the existence of Doppler Effect,the resonance frequency obtained by processing is larger on one side and smaller on the other side.(3)The "frequency el ipse" around the detonation source can be plotted by combining the processing method of modal recognition and Doppler Effect.Accordingly,the vibration frequency generated by millisecond delay initiation is taken as the control base frequency,and the frequency offset generated by Doppler Effect is used to realize the frequency directiona l regulation around the detonation source and the active control of blasting vibration.