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.
Fully mechanized caving mining in extrathick coal seams is currently the most efficient mining method. To figure out the mining-induced stress in extrathick coal seams which is significantly different from the normal ones is essential for mining safety. This research is based on the No. 3106 working face of Lu-Zi-Gou coal mine in China, which extracts extrathick coal seams by using the comprehensive mechanized top-coal caving method. According to the elastoplastic theory, a multiforce superposition mining-induced stress model is constructed in this research. In this model, the mining-induced stress is generated by the side coal seam of the stope, including the load formed by the broken roof blocks in the caving zone, the unbroken rock layers in the side of the goaf, and the rock layers in the bending zone. To verify the model, electromagnetic wave CT detection and borehole endoscopy are used to test the coal’s electromagnetic wave attenuation and internal joints. The results indicate that the mining of extrathick coal seams forms internal and external stress fields in the side coal seams of the stope. As the depth increases, the mining-induced stress first increases and then decreases within the two areas. According to the above conclusions, the width of coal pillars and the location of roadways between adjacent working faces can be reasonably determined.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.