Abandoned old mine excavation detection by Electrical Resistivity Tomography

Abandoned underground mine galleries or excavations in general pose important environmental and economic problems when a site is reactivated after being abandoned, because they might create risks for land stability. At the request of a need for a solution for the reopening of a mine (Horne 5 project of Falco Resources in Rouyn-Noranda, Quebec, Canada) future exploitation would start from 600 m deep. Before that reopening, it is very important to determine old mining excavation locations and conditions. The present study is targeting a technological challenge of detecting old and deep mining infrastructure. There is to date no application allowing the detection of underground tunnels or mining galleries at a depth of >80 m due to their depth and small size. Electrical Resistivity Tomography (ERT) is promising given its ability to image the contrasts between rocks and voids, whether these cavities are empty or filled with water or backfill materials. Several 2D and 3D ERT surveys were carried out to explore the abandoned old mining excavations. These ERT measurements highlighted the existence of old mining stopes, confirmed by the geotechnical boreholes performed on site, as well as two known galleries located at an approximate depth of 100 m. Overall, the results of this study highlight the potential of ERT approaches for the characterization of deep underground excavations.