Experimental Study on The Effect of Charge Structure of Blasting on Damage to Dirt Band in Thin Coal Seam

Abstract

Abstract Based on the coalmines with thin coal seam containing hard dirt band in Shandong Province, aiming at the problem of difficult mining caused by hard dirt band in the process of thin coal seam mining, the damage to hard dirt band by blasting in different charge structures was studied. According to the propagation law of blasting stress wave in coal and dirt band in different charge structures, an experimental platform was set up, and the damage characteristics of dirt band by blasting stress wave under the action of ordinary charge blasting and shaped charge blasting were studied through similar simulated comparative tests. The results show that in the ordinary blasting, the cracks spread out disorderly along the radial direction of the blasting hole and the damage of the dirt band is not so good; however, in shaped charge blasting, the peak stress increases 1.32 times in the direction of energy accumulation, while decreases 22% in the direction of non-energy accumulation, making the explosive energy more concentrated in the dirt band and forming a long and wide directional main crack in the dirt band.