| With the increasing scale of deep hole bench blasting in open-pit mine,the hidden danger caused by blasting vibration is more obvious.How to reduce the damage of blasting vibration becomes particularly important.Based on the open pit blasting project of Anshan GUANBAOSHAN iron mine and surrounding mines in Anhui Province,the blasting vibration effect and zonal blasting technology of open-pit mine are studied by theoretical analysis,numerical simulation and field test methods.The measured blasting vibration signal is decomposed and de noised based on the improved local mean decomposition method,and the signal energy is analyzed by combining Hilbert transform.The main contents and conclusions are as follows:(1)The noise reduction effect of the improved local mean decomposition method combined with wavelet threshold method is studied.The simulated signal and the field measured signal are used respectively,and the signal-to-noise ratio is increased by 9.7 d B and 8.6 d B respectively.The parameter selection of adaptive complementary set local mean decomposition method is studied,and the decomposition parameters suitable for bench blasting vibration signal of open-pit mine are obtained.Combined with Hilbert transform,the energy distribution of blasting vibration signal with time and frequency is obtained.(2)Based on the adaptive complementary set local mean decomposition method,the vibration effect of Open-pit Bench Blasting is analyzed.The attenuation law and energy frequency band distribution of blasting vibration velocity and vibration level are studied respectively.The analysis shows that the attenuation rate of vibration velocity and vibration level is different,and the attenuation rate of vibration velocity is much higher than that of vibration level.The distribution of vibration velocity energy and acceleration energy is also different,the vibration velocity energy is mainly distributed in 0 ? 100 Hz,and the acceleration energy is mainly distributed in 0 ? 200 Hz;the blasting vibration energy concentration is different in different ranges,the velocity energy in the near area is concentrated in the radial direction,the far area is concentrated in the vertical direction,and the acceleration energy distribution is relatively average.(3)The theory of delay blasting and the calculation formula of delay time are summarized.According to the semi empirical formula,the reasonable delay time of zone blasting is 25 ms ? 40 ms.Huygens principle is used to analyze the vibration reduction principle of zonal blasting.The results show that the seismic wave front of zonal blasting is stepped,which can effectively control the distribution range of seismic wave energy.(4)ANSYS / LS-DYNA was used to simulate the vibration reduction effect of different delay time zone blasting.The simulation results show that the vibration reduction effect of double hole zone blasting and simultaneous blasting under the delay time of 25 ms,30 ms,35 ms and 40 ms delay time is respectively simulated.The simulation results show that the vibration reduction effect of 40 ms delay time is the best,the maximum vibration reduction rate of combined speed is 34.8%,and the maximum vibration reduction rate of vertical direction is 27.3%.(5)The delay time of 40 ms is verified by engineering,and the comparative analysis of hole by hole initiation and double hole zone blasting is carried out.The field measured blasting signals show that the vibration velocity in three directions near the blasting area can be reduced by using the zonal blasting,and only the vertical vibration velocity can be reduced in the far zone.From the point of view of energy,the energy of zone blasting is more distributed in high frequency band than that of hole by hole blasting,which is beneficial to avoid the natural vibration frequency of buildings. |
PDF Full Text Request