A variable density explosive for open pit mining

In many large open pit mining operations the explosive product line of choice over the last decade has been heavy ANFO blends ranging from 20 to about 50 percent emulsion. The amount of emulsion used depends upon both application and explosive requirements. Two properties of these blends that change considerably with the blend ratio, are water resistance and density. For good water resistance, about 50 percent emulsion must be used. However, the 50/50 blend has the highest density, ranging from 1.30 to 1.40 g/cc, and the largest critical diameter. This paper presents a case study in the application of a chemically gassed, lower density 50/50 blend in an open pit coal mine. This product had the required water resistance and the flexibility to adjust loading density and powder factors to match the mining applications. Ambient densities ranging from 0.80 to 1.20 g/cc were evaluated.