Restudy on effectivty of direct current advance detection method in roadway

The direct current (DC) advance detection method in coal mines is one of the main methods for detecting water-rich anomalies in front of excavation face. It has ahistory of nearly 30 years in coal mines of China. Some experts and scholars have questioned the effec⁃ tiveness of this technology through research and analysis. Based on the infinitely extending plate， sphere or cube model in a uniform whole space， the relationship between the abnormal distance and the minimum value of the abnormal characteristic parameter was fitted by calcu⁃ lating the potential distribution and the full space of the point power supply， and the extraction method of abnormal characteristic parame⁃ ters， the response characteristic of the abnormal under floor were analyzed， and the theoretical detection distance was calculated.The re⁃ sults show that:the abnormal physical energy in front of the tunneling work produces obvious abnormal response behind the roadway， that is， the rear signal contains information of low-resistivity body in the front， which proves that the basic principle of this technique is cor⁃ rect.The front low-resistivity body is not a mirror image of the rear apparent resistivity abnormal position. The front abnormal position can be obtained by selecting the correct abnormal characteristic parameters.Both the low-resistivity bodies in front of the roadway and the low- resistance body of the floor can generate potential anomalies， which can be identified according to different characteristics of abnormal re⁃ sponse. The maximum distance of DC advanced detection method can reach about 80 m.The DC advanced detection method in the excava⁃ tion face of the coal mineis effective and can be popularized and improved continuously.