Study of advance elaborate detection with transient electromagnetic method for mine with closed poor boreholes

Closed poor boreholes connect aquifers at some degree to form well concealed water diversion channels, which poses a water hazard threat on either tunneling or working bench recovery. In order to discuss the effectiveness of using the transient electromagnetic method in the advance detection of closed poor boreholes for the mine, the 3D geologic-geophysical model of the closed poor boreholes in front of the tunneling working bench was established based on the full-space transient electromagnetic theory to simulate and study the response characteristics of the full-space transient electromagnetic field in the influence area model of closed poor boreholes. As indicated by the numerical simulation results, the enhanced amplitude and obvious anomaly characteristics of the aquifer body near closed poor boreholes were shown in the induced electromotive force (EMF) multi-channel diagram. As indicated by the detection results, in combination with the study about the application in the advance detection work of closed poor boreholes in front of the tunneling working bench for the I0104₁08 working bench haulage way in Shuangma Coal Mine, Ningxia, there was local low resistivity at the coal seam roof near the borehole, indicating that the certain hydraulic conductivity of the borehole led to the enhanced relative local high water abundance of the coal seam roof. According to the study result, the local water abundance enhancement caused by the closed poor boreholes can lead to typical and recognizable transient electromagnetic field response. Adopting the transient electromagnetic method in the advance detection for the mine, in combination of elaborate processing and interpretation, the relative water abundance characteristics of the rock formation near the borehole can be effectively found out, and then the hydraulic conductivity of closed poor boreholes can be evaluated, providing basis for the governance of closed poor boreholes and guaranteeing the safe production of the mine.