Subsurface hazardous environments and hydrological threats in underground mines: an OCTEM detection case study

The extraction of mineral resources has progressively transitioned from shallow and easily accessible deposits to deeper and more challenging ores, thereby increasing the complexity and concealment of mining environments. The Opposing-Coils Transient Electromagnetic Method (OCTEM), an enhanced version of the Transient Electromagnetic Method (TEM), offers notable advantages, including rapid measurement times, strong penetration capabilities, high efficiency, and minimal influence from surface terrain. This study used Tongkeng Mine, situated in the karst topography of Southwest China, as a case study to evaluate the effectiveness of OCTEM in detecting concealed disaster-prone zones and hydrogeological characteristics within mines. The results indicated the following: (1) Periodic underground monitoring of caving zones and goafs using OCTEM could facilitate the safe extraction of minerals. (2) OCTEM proved highly effective in detecting surface subsidence in previously repaired collapse areas. (3) OCTEM demonstrated promising potential for preliminary screening and investigation of hidden karst caves and goafs resulting from unregulated mining activities in karst regions, thereby reducing reliance on traditional, experience-based drilling methods and lowering exploration costs. Overall, this study effectively contributed to reducing safety maintenance costs and enhancing the economic benefits of mining operations.