双临空面条件下隧道爆破近区振动波形构造与应用

近年来基于单孔爆破振动数据进行微差振动合成计算是研究的热点。为解决第二临空面形成后波形计算问题,以莲塘小净距隧道为工程背景,设计现场爆破试验获取双临空面下单孔波形;利用小波包变换分析实测波形的优势频带,将单孔波形分解为各优势频带的多个子波;通过拟合得到炮孔药量、爆心距与各频带子波最大振速峰值的函数;利用该函数获取全部炮孔在不同频带的子波,叠加所有频带子波构造出各孔单孔波形;由此计算炮孔位置、药量变化下不同微差爆破合成振动波形,得到最优孔间延时。结果表明:计算所得合成波形与实测波形在频率组成和波形趋势上相吻合,各振速峰值误差小于0.3 cm/s;周边孔延时为6～7 ms时减振效果最佳,现场应用效果良好。

Construction and application of near zone vibration waveform of tunnel blast under condition of double-free face

In recent years,millisecond vibration synthesis calculation based on single hole blasting vibration data is a research hotspot.Here,to solve the problem of waveform calculation after formation of the second free face,taking Liantang small clear distance tunnel as the engineering background,the onsite blasting test was designed to obtain the single hole waveform under condition of double-free face.The dominant frequency band of the measured waveform was analyzed with the wavelet packet transform,the single hole waveform was decomposed into multiple wavelets of dominant frequency bands.By fitting,functions of blast hole charge,blast center distance and the maximum vibration velocity peak of each frequency band’s wavelets were obtained.These functions were used to obtain wavelets of all blast holes in different frequency bands,and wavelets of all frequency bands were superimposed to construct all holes’single hole waveforms.Then,the synthetic vibration waveform of different millisecond blasts under changes of blast hole position and charge quantity was calculated,and the optimal time delay between holes was obtained.The results showed that the calculated synthetic waveform is consistent with the measured waveform in frequency composition and waveform trend,and the error of each vibration velocity peak is less than 0.3 cm/s;when the time delay of peripheral hole is 6-7 ms,the vibration reduction effect is the best,and the onsite application effect is good.