Permeability Increase with Deep Borehole Controlled Pre-cracking Blasting Technology in Low Permeability and High Gassy Seam

In order to solve the difficult gas drainage problem in low permeability and high gassy seam,the RFPA2D numerical simulation software was applied to establish two deep borehole controlled pre-cracking blasting mechanics models.With the comparison and analysis on the simulation results,a set of blasting parameters obtained which were suitable for floor gas drainage in No.8 mine of Hegang Coal Mining and the site trial with the parameters was conducted.The results showed that after the blasting,the average value of the seam permeability coefficient reached at 2.23 m2/(MPa2·d)and 3.05 times higher than the average value of the seam in-situ permeability before the blasting conducted.Thus the technology could obviously improve the cracking development degree of coal around the borehole and could improve the permeability of the seam.The target to improve the seam gas drainage value and the gas drainage rate could be reached.