Ground Probing Radar was used in three Canadian mines to assess the feasibility of enhancing mine planning techniques in order to reduce mining cost and increase production. It is shown that GPR provides reliable results regarding detailed mapping of mine geology and structural integrity in backfilled areas.
Le georadar a ete utilise dans trois mines au Canada afin d'evaluer la possibilite d'ameliorer la planification minière en ce qui concerne la reduction des coûts et l'augmentation de la production. Nous montrons que la technologie georadar produit des resultats fiables relativement à la cartographie geologique et la surveillance de I'integrite structurelle des remblais.
Grund Pruefender Radar wurde in drei Kanadischen Bergwerken gebraucht, um die Ausfuehrbarkeit von verbesserten GrubenEntwurfstechnik zu schatzen und somit Grubenkosten zu verringern, und die Produktion zu erhöhen. Es zeigt sich dass GPR zuverlassige Ergebnisse Iiefert, hinsichtlich von ausfuehrlicher Planung von Bergwerk-goeologie und in der Vollstandigkeit der Struktur in den wieder aufgefuellten Gebieten.
The Canadian mining industry is faced with unprecedented challenges because of falling base metal prices as a result of international competition and diminishing ore reserves. To survive, the industry must therefore mine efficiently and safely at ever increasing depths. This approach requires that new planning methods be developed to reduce the cost of mining and keep a high standard of safety. One method that is being applied and tested in two underground hard rock mines in Quebec and Ontario is Ground Probing Radar (GPR). The radar technology has been used in the past few years in many geotechnical applications to assess concrete quality and pavement integrity (Momayez and Sadri 1993), map old burial grounds to search for graves (Momayez 1993) and determine the depth of bedrock in routine site investigation campaigns (Davis and Annan 1987). The applications of GPR in mining engineering have been limited in number because of its recent introduction in the industry as a monitoring and investigation tool. This paper introduces the radar technology, its principle and operation, and presents three case studies where radar was used to determine whether it can assist the mine personnel in the planning of new areas of the mine.
The basic principle in Ground Probing Radar is fairly simple. As shown in Figure 1, the radar antenna transmits a short electromagnetic pulse of radio frequency into the medium. When the transmitted wave reaches an electric interface, some of the energy is reflected back while the rest will continue its course beyond the interface. The radar system will then measure the time elapsed between wave transmission and reflection. In modern systems, this is repeated at short intervals while the antenna is in motion and the output signal (or scans) are displayed consecutively in order to produce a continuous profile of the electric interfaces in the medium. In general, the propagation speed of the wave and its reflection are affected by the dielectric constant and the magnetic susceptibility of the medium. The electrical conductivity of the medium contributes to the attenuation of the wave and to some extent to its reflection. The antenna wavelength affects the ability of the system to identify objects of different size. For example, high frequency antenna have better resolution, but shallow penetration depth, while low frequency antenna have a coarser resolution, but penetrate deeper into the medium.