Dynamic Effect of Shaped Charge Blasting and Its Application in Coal Seam Permeability Enhancement

The dynamic effect of shaped charge blasting and its application in coal seam permeability enhancement have been investigated. Comparative experiments of shaped charge blasting and conventional blasting to fracture the concrete are carried out. Then, the propagation characteristics of explosion stress waves under shaped charge blasting and conventional blasting are analyzed by ANSYS/LS-DYNA. Finally, the fracture mechanical model of shaped charge blasting is established. The experimental results show that the width of the four main cracks formed after conventional blasting is 0.3 cm, while the width of the cracks in the energy accumulation direction after shaped charge blasting is 1.1 cm and the width of that in the vertical energy accumulation direction is 0.4 cm. The numerical simulation results show that the crushing area after shaped charge blasting is "dumbbell type", and the area is smaller than that of conventional blasting. However, the cracking area is "spindle type", and the development of the fracture degree is better than that of conventional blasting. In addition, shaped charge blasting is used to improve the permeability of coal seams. The results show that shaped charge blasting effectively improves the permeability and gas extraction rate of coal seams.