An acoustic wave method for evaluating the effectiveness of blast to enhance fragmentation in longwall top coal caving

Abstract

AbstractThe advanced deep hole blasting (ADHB) is commonly used to improve the fragmentation of thick hard top coal in longwall top coal caving (LTCC) mining. This paper presents an acoustic method to quantitatively evaluate the effectiveness of the ADHB. First, the variations of P‐wave velocity of hard coal samples under uniaxial and triaxial compression are obtained from the laboratory acoustic test. Then, an acoustic wave method based on seismic tomography is proposed to assess the effectiveness of the ADHB by introducing the P‐wave velocity attenuation model into the data processing. Finally, a field seismic tomography test is conducted to obtain the distribution of the P‐wave velocity of top coal before and after the ADHB implementation. And the P‐wave velocity attenuation is calculated to estimate the fragmentation effectiveness of ADHB. The results indicate that the P‐wave velocity attenuation model could well represent the broken degree of hard coal, suggesting that the proposed acoustic wave method could quantitatively evaluate the fragmentation effectiveness by exporting the nephogram of P‐wave velocity attenuation. The present study may provide technical support for improving the recovery ratio of thick hard top coal for LTCC mining.