| Drilling and blasting method has been widely used in tunneling construction with high efficiency and economy,but the vibration problem caused by it can not be ignored.Blasting vibration signal reflects the vibration characteristics of vibration particle after explosion of explosive,and is an important data to judge the impact of blasting vibration on structures.Through the combination of signal analysis technology and numerical simulation of field monitoring data,the vibration effect of the blasting site can be fully understood and studied,the applicability of blasting scheme and blasting parameters can be evaluated,and the reference basis for reasonable blasting construction can be provided,so as to minimize the impact of blasting vibration on surrounding structures without affecting the blasting effect..On the basis of Engineering measurement,this paper uses HHT signal analysis technology to analyze the frequency spectrum characteristics of blasting vibration signals for different surrounding rock construction,and accurately identifies the initiation time of milliseconds delay at different positions by instantaneous energy spectrum.ANSYS is used to analyze the frequency spectrum characteristics of blasting vibration signals for different surrounding rock construction.LS-DYNA simulated the influence of two kinds of surrounding rock blasting on the vibration velocity of different particle in existing tunnel under the same charge quantity.The main work and achievements are as follows:(1)According to the statistics of blasting vibration signals in full-section construction of surrounding rock III and step-up construction of surrounding rock IV,the maximum peak velocity of particle is in the radial direction,and the peak velocity of particle basically depends on the maximum explosive charge quantity of the first single-shot.The reason is that the cut hole is deep,the charge quantity of single-hole is large and the face of blasting is less than that of the subsequent section.(2)The three-dimensional combined time-frequency spectrum,instantaneous energy spectrum and Hilbert spectrum of vibration signals in blasting of surrounding rocks III and IV are analyzed by HHT.For multi-stage millisecond delay blasting,the instantaneous energy in MS-1 section is the largest,the frequency band is wider than that in other sections.The vibration frequency basically distributes between 50 HZ and200HZ.The frequency of blasting of surrounding rocks III is concentrated between 50 and 350HZ,the high frequency component increases,and the frequency of subsequent sections increases.The rate energy is also higher,and the vibration frequency under the two conditions is higher than the natural frequency which easily resonates with the building,which indicates the applicability of the blasting scheme.(3)The instantaneous energy spectrum of HHT is used to accurately identify the initiation time of each section.Compared with the actual initiation time and the theoretical initiation time,the section explosion is within a reasonable range.It showsthat the instantaneous energy spectrum of Hilbert can guide the blasting construction and play a role in predicting the serial or delayed blasting.(4)Linear Regression Analysis of III and IV Surrounding Rocks by Sadovsky’s Empirical Formula.(5)ANSYS LS-DYNA software is used to simulate blasting under surrounding rocks of type III and IV.The peak vibration velocity of particle appears in the area between arch waist and arch foot at the nearest section of the blasting center on the blasting side of existing tunnel,and then gradually diffuses around.The radial velocity and tangential velocity of particles are the largest.In the case of the same explosive quantity,the three-dimensional peak velocity of the core distance from the nearest arch waist particle of the third wall rock is larger than that of the fourth wall rock,which is basically the same as the field measured vibration law.Compared with the peak velocity of the simulated node,the simulated radial velocity is 12.5% higher than the measured value,and the vertical velocity is higher than the measured peak velocity,so the simulated value is relatively safe. |
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