Blasting methods to improve rock fragmentation

Abstract

A method to improve rock fragmentation with explosives is based on a new way of explosion energy transfer to the solid media. It provides a considerably higher efficiency of the explosion energy by changing the gas dynamic processes of the expansion of detonation products in the charge chamber. In practice this method has been instrumental in developing two new types of charges: the air-spaced charge for rock fragmentation and the air-cavity charge for heaving blasts. The basic idea underlying charge construction in both types consists of a most efficient transfer of explosion energy into rock fragmentation or heaving process by reducing the initial peak pressure and increasing the time of explosive action upon the rock mass. When exploding such charges, shock waves and gas streams undergo gas dynamic interactions in air cavities causing the rock to be repeatedly loaded with a system of shock compressions. This makes it possible to reduce energy losses due to too fine rock fragmentation in the zone next to the charge, as well as to increase the amount of energy directed for a more even breakage of the entire rock material. An application of the new types of charges in both construction and mining industry increased the excavator efficiency by 20–40%, reduced the specific consumption of explosives by more than 20%, diminished seismic influence of explosions, etc. The new method of rock fragmentation described here paves the way for further development of the theory and practice of blasting operations yielding a higher efficiency of the use of explosions.