Mining Publication: Electromagnetic Location Systems for Metal/Non Metal Mines

Characteristics of metal-nonmetal mines were evaluated to determine the suitability of applying the Bureau of Mines electromagnetic (em) location system to the problem of locating trapped miners. Statistical distributions of mine depths and overburden conductivities show that the existing Bureau em system is inadequate for most metal-nonmetal mines. Alternate approaches to trapped miner location in deep mines were identified, and subsequent field tests were conducted at six mines to evaluate their feasibility. The approach considered to be the most promising is one that uses the existing backpack transmitting system, modified slightly for a dual frequency output, in conjunction with a sophisticated signal processing receiver on the surface. The main advantage of staying with a "through-the-earth" approach is that the underground equipment can be kept simple, easily maintained, lightweight, and inexpensive.