Study on the hard top coal crushed by blasting

Based on the prototype of caving coal under the metal nets and caving coal on total high in hard coal of Datong,the rules of charging decoupling coefficient and explosive charge along line influencing the size of top-coal lump were researched through the virtual blasting experiment in perpendicular to coal stratification and parallel to the coal stratification. And the conversion formula of quantity of explosive between model and prototype was presented. The relations between the size of coal lump fractal, surface cranny fractal and density of blasting energy were roughly analyzed by means of the fractal geometry theory. Try to find out the rational parameters of explode and construction for blasting the hard top coal in coal mine, and gain that the possibility of the top-coal caving would be enhanced when the value of K e is smaller than 1.2 under condition of the blasting of perpendicular to coal stratification and bigger than 1.2 under condition of the blasting of parallel to coal stratification.