New mass blasting technology for complex orebodies

Efficient mining of complex orebodies means maximal extraction of ore at minimum loss and dilution. Complex orebodies occur in nonuniform rock masses composed of rocks of different acoustic stiffness and strength. Blasting of such orebodies induces mixing of ore and barren rocks at their interfaces, and ore gets diluted with barren rocks. Reducing ore and barren rock mixing is only possible through a decrease in the width of the blast muck pile with regard to ore and rock distribution in it. It is proved that efficiency of complex orebody mining depends on obtaining of ore and nonmetallic rock muck piles. It is found that in blasting at complex faces, it is very important to increase the duration of the stress wave and reduce the peak pressure of the gaseous products of explosion, thereby increasing the destructive effect of the blast. A new technology of blasting is proposed using borehole charges composed of a mixture of industrial explosives and expanded polystyrene granules. The technology ensures decrease in the limiting pressure of gaseous blast products, increase in the duration of the blast impact onthe treated medium, and creation of a cut-off gap (artificial air barrier) along the contour of standard-grade and substandard ores. This helps reduce the degree of their mixing and obtain standard-grade and substandard ore muck piles of different shapes and sizes.