Similarity Test Study On High - Level Throwing Blasting

In order to investigate the influence law of blasting effect and bench slope velocity distribution along with the change of blasting parameters in high bench cast blasting. The similarity criteria of smaller bench model test were deduced upon similitude theory and dimensional theory, a series of bench model made from a certain proportion of cement mortar were blasted, Influence of specific charge, line of least resistance and dip angle of hole on blasting effect were respectively studied, the loose coefficient of rock, the furthest distance of throw and effective throwing rate after explosion were studied with statistics. Meanwhile, the bench slope in the course of the model blasting experiments were observed using high-speed photography system. The bulge outline and the law of rock motion on bulge surface center were obtained, and the laws of speed change of tracking points were analyzed. Model experimental study shows that the furthest distance of throw and effective throwing rate increased with specific charge increased, and the increasing trend gradually slow down, but they decreased with dip angle of hole increased, and the decreasing trend gradually got faster, effective throwing rate increased at first, then decreased with line of least resistance increased. For prototype, specific charge was 1.00～1.20 kg/m3, line of least resistance was 7.5m and dip angle of hole was 65～75° should be suitable. High-speed photography observation suggested that bulge surface center velocity showed a characteristic of acceleration- uniform speed- the second acceleration-deceleration. The initial speed formula of projectile wasv₀= f（QL,W）=λ(Q_L^1/2/W)xW²,and the projection angle formula was Under the blasting scheme in this paper, the furthest distance of throw was 118m, the maximum speed of throw was 27.522m/s, and the permissible safety distance between blasting popping rock and equipment （building） was 121.54～153.50m. The result of model test obtained provide theory basis for the optimum design of high bench cast blasting and prediction of blasting effects.