The utility of rock-bolts as long electrodes for underground ERT surveys in mine settings

The aim of the study is to analyse the effectiveness of rock-bolts applied as electrodes in Electrical Resistivity Tomography (ERT). ERT surveys were carried out with the use of expansive rock-bolts mounted on the roof of a copper mining excavation in Poland. The application of rock-bolts as electrodes renders ERT surveys more cost efficient and less time consuming than ones employing standard electrodes that require drilling and mounting in the rock mass. In order to analyse the utility of expansive rock-bolts, comparative surveys were carried out on the surface and in another mining excavation with geological and mining conditions similar to the excavation where expansive rock-bolts were used. The results of surface tests show that there is only a slight difference in resistivity distribution between surveys carried out with the use of standard, short electrodes and the long ones. For results obtained during the surface tests, a statistical analysis was applied. The surveys carried out in both excavations delivered similar information about the distribution of the main anomalies located over the roofs. The goal of ERT surveys carried out in mining conditions was to detect the fractured zones which might be sources of outflow of gas and/or water to the excavations.