Research Article

Blasting for Fracturing and Improving the Permeability of Deep, Soft, Outburst Prone Coal Seams Using Blasthole and Relief Hole Drilled into the Underlying Stratum: Optimal Hole Distance

Table 5

The parameters of fracture area ratio.

Mining depthSingle blast hole3 times hole spacing5 times hole spacing7 times hole spacing

0 m10.06%12.50%13.55%12.55%
1000 m1.85%10.78%6.63%3.14%
1500 m0.47%2.39%1.07%1.02%