3D geological radar and its applications in coalfield fault fracture zones

Identifying the type, location and distribution of geological bodies in advance is crucial to ensure safe and efficient coal mining. Referring to the limitations of traditional 2D ground-coupled Ground-Penetrating Radar (GPR) in determining the direction and orientation of geological anomalies such as fault fracture zones, along with the significant safety risks associated with close-range detection near the working face in underground coal mines. A spatial scanning 3D GPR method is proposed for determining the position and orientation of concealed hazardous geological structures ahead. Firstly, by drawing on the theoretical model of fault fracture zone approximating to actual conditions, the forward numerical simulation was carried out using the finite difference method to analyze the time-domain response of fault fracture zone under different filling conditions. Secondly, a case study was performed on the Lvtang coal mine with complex geological conditions. Air-coupled 3D GPR was used to repeatedly collect multi-angle and multi-directional data from the +1730 horizontal transportation roadway of the mine. The advanced detection results were interpreted through time-profile analysis and comparative analysis of vertical and horizontal slices. Finally, the predictions for the orientation of hidden disaster-causing geological body were validated based on drilling and field exposure data. Results show that the underground application of air-coupled 3D GPR could accurately identify the geological body of the fault fracture zone within a 30-meter range in front of the mine. Filtering and wavelet transform techniques could extract valid wave information from signals with low signal-to-noise ratio. When combined with forward numerical simulation, they enabled a more accurate interpretation of the actual detection profiles. This study provides a practical basis for the further development and application of 3D GPR in the advanced detection of hidden geological bodies in coalfields.