Twenty years of Ground-probing radar in salt and potash mines

Radar has been used for twenty years for underground exploration of the boundaries and internal structures of salt deposits in Germany. The method and equipment, developed by the Federal Institute for Geosciences and Natural Resources (BGR) in cooperation with the German mining company Kali und Salz AG in the early 1970s, make it possible to determine the distance to stratigraphic boundaries up to 1000 m from the antenna, especially in anhydrite, claystone, and basalt, and between joints filled with water or brine. The equipment is light weight and battery powered; it can be used almost anywhere in a mine without any preparatory measures. Therefore, the method is very economical. The location of the reflecting discontinuities may be determined using additional directional antennae. For exploration preparatory to mining, various probe systems have been developed for use in drillholes. In cooperation with Prakla-Seismos AG, a special GPR probe was developed for deep boreholes. Salt domes have been explored down to depths of 3000 m with'this probe. A probe has been developed for use in boreholes in mine drifts. This probe is designed so that it is safe to use in mines in which there is the risk of explosions. It is equipped with a directional antenna so that the spatial orientation of the reflecting planes can be determined. The technical aspects of the equipment are discussed and the results of exploration in German and Canadian salt deposits using the radar method are used as examples.