Blasting parameter optimization of medium-depth hole caving for steeply inclined thin veins

On the basis of the industrial experiment of medium-depth hole caving in Jinchanggouliang Gold Mine, the authers carried out the optimization research of hole pattern blasting parameters. ANSYS/LS-DYNA was used to make several schemes of numerical simulation. Then the distribution features of the blasting stress fields under different hole pattern parameters and the formation process of the fractured blasting regions under the constrained blasting effect of narrow vein were obtained. The results show that when the resistance line is between 0.8 and 1.2 m, under the same hole spacing, the effective stress peak of the central free surface decreases with the increasing resistance line; when the hole spacing is between 0.9 and 1.6 m, it increases with the rising hole spacing under the same resistance line. As the bore hole density coefficient increases, the stress increments slow down, and the ore loss and dilution aggravate, if the bore hole density coefficient is more than 1.5. Comparison of all the schemes displays that the 1.0 m×1.4 m hole pattern parameter is the best. After employing the optimization results for the field experiment and with the CMS evaluating the blasting effect, the actual blasting zone volume covers 91.8% of the designed volume. The blast, with sound effect, did not cause the top and bottom side wall orebody to cave.