EXPERIMENTAL STUDY ON DAMAGE CHARACTERISTICS OF DIRT BAND BY SHAPED CHARGE BLASTING IN COAL SEAM

Blasting technology is one of the effective methods to deal with the complex problems in coal mines. In order to solve the mining difficulties caused by the failure of the dirt band to be broken by the shearer in the mining process of coal seam containing dirt band, based on the ordinary deep hole blasting, a study on the damage of dirt band by shaped charge blasting for coal seam containing dirt band is carried out. In this paper, the fracture mechanics model of dirt band in shaped charge blasting is established, and the evolution law of crack and propagation law of blasting stress wave in dirt band and coal by ordinary blasting and shaped charge blasting are analyzed. By introducing the gain coefficient and the decrease coefficient of stress wave intensity in the direction of energy accumulation and non energy accumulation, separately, the calculation equations for the relationship between the range of crushing area and the stress peak value of ordinary blasting and shaped charge blasting in different directions are deduced. The mechanical properties of two identical specimens under the action of ordinary charge blasting and shaped charge blasting are systematically investigated by similar simulated experiment. The experimental data are basically in agreement with the theoretical calculation results. The research results can provide theoretical support for the weakening of dirt band by shaped charge blasting in coal seam containing dirt band.