Forward Modeling for the Fine Detection of Geological Abnormal Area in Coal Seams Using High-frequency Radio Imaging Method

The radio imaging method (RIM) can be used in underground mines to identify geologically hazardous areas; however, it does not yield accurate results. To address this issue, a high-frequency (1–8 MHz) RIM is proposed here for the fine detection of geological anomalies in coal seams, and its feasibility is evaluated. A reliable forward model is established based on the propagation characteristics of electromagnetic waves in lossy media and the functional relation between the electrical parameters of coal and electromagnetic wave frequency. Numerical simulations were performed using a frame antenna at high frequencies; the field strengths of electromagnetic waves in coal seams with and without geological abnormal areas were compared. The difference diagram demonstrates the field strength attenuation “shadow area” formed by the geological abnormal area. The attenuation coefficient, wavelength, and far-field radiation characteristics of the frame antenna were used to discuss if the detected geologically hazardous location is accurate. The feasibility of high-frequency detection is further supported by the electromagnetic wave signal strength in the receiving tunnel.