Prediction of the Penetration Radius of Cumulative Blasting.

To improve the efficiency of coal seam gas extraction, the influence characteristics of different factors on the penetration effect of cumulative blasting were determined and the hole spacing was effectively predicted; in this work, we used ANSYS/LS-DYNA numerical simulation software to establish the penetration model of cumulative blasting. Combined with an orthogonal design scheme, the crack radius prediction of cumulative blasting was studied. A prediction model for predicting the fracture radius of cumulative blasting based on three groups of different factors was established. The results showed that the primary and secondary order of factors that affected the fracture radius of cumulative blasting was as follows: ground stress > gas pressure > coal firmness coefficient. The penetration effect decreased with increasing ground stress and decreased with an increase in the gas pressure and coal firmness coefficient. The industrial field test was carried out. The gas extraction concentration increased by 73.4% after cumulative blasting, and the effective crack radius of cumulative blasting was approximately 5.5-6 m. The maximum error of the numerical simulation was 1.2%, and the maximum error of the industrial field test was 6.22%, which proved that the crack radius prediction model of cumulative blasting was correct.