Application of Audio Frequency Electrical Penetrative Imaging Technology for the Detection of Karst Features of the Ordovician Limestone in Coal Mines, North China

Ordovician karst water in the floor of working faces is the major water hazard threatening coal mining operation in North China type coalfields, also a major water hazard source in large scale coal mines in China. The paper presents audio frequency electrical penetration technology adopted at present into China's coal mines. The technology based on the theory of full space DC electrical field, adopted stratified imaging by VL frequency electrical field, realized imaging of karst aquifer distribution in the floor of working face. The paper, also with the technology as the core, presents geophysical technical framework for Ordovician karst water control in China's underground coal mines, and the effect of detection by the technology in dewatering and reinforcement of floor in combination with some engineering examples.