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The transient electromagnetic method (TEM) for boreholes uses fixed source loops to launch at excavation faces, and is able to realize the mobile reception of secondary fields in the boreholes and detections of low-resistance hazards. This method is known as high detection accuracy, due to the fact that the receiving points are close to the anomalies. However, the interpretation method for this device has not yet been perfected. The present study's goal was to realize the interpretations of boreholes TEM based on inverse transform algorithms of the TEM wave-fields and full waveform inversions. It was found that under the conditions of transient electromagnetic virtual wave-fields, the characteristics of the virtual wave-field time-distance curves of the two-dimensional device could be examined, and a corresponding dynamic correction algorithm was successfully obtained. The wavefield velocities were analyzed using an equivalent conductive plane method. Additionally, the pseudoseismic inversions of the tunnel-borehole TEM data were realized using full waveform inversion technology. Then, the inversion results of the three-dimensional numerical simulations, flume physical simulations, and downhole field simulations were calculated. It was observed that good imaging results had been obtained for small-scale borehole radial anomalies. Finally, the proposed method was applied to the engineering practices in an underground coal mine in Shanxi Province. The practicability and effectiveness of the proposed method in the fine detection of the properties, forms, and scale of waterlogged goaf roadways were successfully tested in the field. The research results indicated that the roadway-borehole transient electromagnetic detection method was complementary to the underground geophysical exploration and drilling, and could be effectively applied in the detection of waterlogged goaf roadways. [ABSTRACT FROM AUTHOR]

T he geological transparency of working face is the premise and guarantee to realize the intelligent and accurate mining for coal resources. A large number of gas drainage holes, water exploration holes and other boreholes are constructed before and during coal mining. In this paper, the borehole radar (BHR) is used to detect the coal bedding interface in boreholes along the coal seam. With gprMax, we analyze the conditions of the top and bottom interface of coal bedding with 100 MHz and 200 MHz BHR at an dip angle of 0°;analyze the response characteristics of the 200 MHz BHR when the dip angle is 15°, 30°, 45°, and 60°;analyze the influencing characteristics of roadways and bolts during BHR detection.Practical applications are carried out.The result shows that 1) when the borehole inclination is 0°, to distinguish the reflected wave of roof from that of floor, for 100 MHz borehole radar, ΔD needs to be greater than 1 m, and for 200 MHz borehole, it needs to be greater than 0.5 m. 2)When the drilling inclination angle is not 0°, the reflection profile of the top and bottom interface will have a cross feature, and the greater the dip angle, the greater the crossing angle. 3) BHR multiples in boreholes along coal seam have nothing to do with borehole position and inclination angle, but are related to dominant frequency of BHR;4)The change of aperture mainly affects the in-phase axis shape of direct wave. 5)the roadways and bolts have an impact on the detection of coal -rock interface.6)The position of roadway reflection event axis is only related to the nature of coal seam. Therefore, the electromagnetic wave velocity of the coal seam can be calculated by calculating the slope of the event axis. The actual detection of coal seam thickness of about 3 m using 200 MHz in a mine in Shanxi province shows that the electromagnetic wave propagation speed in the coal seam in this area is 0.1342 m/ns. With the proposed processing method,the accuracy of BHR results is high, the error is within 0.5 m.Combined with the borehole trajectory, the BHR can provide accurate coal seam interface position information for the transparent working face. • BHR can be used to detect coal formation interface, combined with borehole trajectory, it provides the interface information for transparent working face. • The response characteristics of coal formation interface detected by BHR in horizontal wells in coal mine is quite different from BHR detect in ground vertical hole. • The electromagnetic wave velocity of coal seam can be calculated by using the reflected wave of tunnel. • The migration imaging method of coal seam roof and floor is proposed. [ABSTRACT FROM AUTHOR]