Study of Evolution of Propellant-Blasting Vibration Wave in Coal

Abstract

Propellant blasting has a wide range of application scenarios in coal-bed methane mining, but relatively few studies have been conducted on the propagation and attenuation laws of its blasting vibration waves. In order to better understand the composition and attenuation law of vibration waves produced by propellant blasting, the blasting vibration test of solid propellant was carried out by using imitation coal. Firstly, this study analyzes the composition of propellant-blasting vibration wave components using polarization theory in seismology. Secondly, the vibration velocity peak and duration of the propellant-blasting vibration wave were analyzed. Finally, the distribution law of propellant-blasting vibration energy in the frequency domain was analyzed using the wavelet packet technique. The results showed that the propellant-blasting vibration wave contains three kinds of waves, namely, P-waves, S-waves, and R-waves. Propellant blasting–induced vibration waves in the coal and P-waves in the near and far areas have a large proportion, which mainly leads to the horizontal vibration of the mass point. The S-wave component accounts for less. As the distance increased, the proportion of R-waves increases and becomes the main factor of vertical vibration of the mass. The vibration velocity caused by propellant blasting is small and the vibration duration is long. The vibration velocity and the vibration duration attenuate slowly with the increase of the distance from the borehole. The propellant-blasting vibration signal is a low narrow-frequency signal. Its energy is distributed in 0–150 Hz, and it is concentrated in 0–78.125 Hz. The dominant frequency of the propellant-blasting vibration wave is at a low frequency in the region farther away from the borehole, and the proportion of low-frequency energy also increases. The research results are expected to promote the application of propellants in the field of coal cracking and permeability enhancement.