Testing method on the effect of blasting releasing pressure based on in-seam wave velocity tomography

The stress anomaly caused by the coal pillar left over from the overlying goaf on the working face results in great hidden trouble to the coal mining.Blasting is a common method to eliminate the stress concentration of the coal pillar, but it lacks the technology to evaluate the blasting effect.The qualitative relationship between the wave velocity of in-seam wave and the stress is analyzed.The twice wave velocity tomography is performed before and after the overlying pillar blasting, and the difference of the wave velocity is calculated to evaluate the pressure relief effect of the coal pillar blasting on the top of the working face.The wave velocity imaging results are compared with numerical simulation, ground pressure monitoring results and actual mining conditions.The results show that the wave velocity of in-seam wave has a good correlation with the stress state of surrounding rock in the working face, and the wave velocity can effectively reflect the stress distribution and transfer, reasonably evaluate the pressure relief effect of coal pillar blasting.