Experimental Study on Permeability Improvement of Deep Hole Pre-splitting Cumulative Blasting in Low Permeability Coal Seam

In order to improve the permeability improvement effect of deep hole pre-splitting blasting, based on the similarity simulation theory, the experimental model of deep hole pre-splitting blasting of low permeability coal seam was established, and the sample was prepared by using the proportion of similar materials. By monitoring the strain signal of coal seam, the crack propagation characteristics of samples under blasting loading are analyzed. The results show that the blasting sample will produce reverse tension unloading wave under the action of explosion compression load, which will cause the crack expansion of the blasting sample and have obvious penetration effect along the direction of energy collecting charge. Field tests showed that the concentration of gas extraction in the coal seam after permeability improvement by pre-splitting cumulative blasting through deep hole was 1.18 to 3.05 times of the original, the gas extraction flow was 1.2 to 3.3 times of that before blasting, and the extraction radius was 4.5 m.