Discussion on problems of direct current advance detection method in roadway driving face

Direct current method is the main method for advanced detection of the current mining face of coal mines. The detection effect is directly related to the s afety of coal mines. In view of the spherical shell theory,an anomalous body model on the side of the point source was established and the three-dimensional potential V alues were calculated,the potential distribution on the other side of the point source was analyzed when there was an abnormal body on the point source, and a model W ith cubic anomalies and infinite plate-shaped anomalous bodies at different distances was established in front of the working face; Through numerical simulation calcula tions,the relationship between the apparent resistivity anomaly range and the actual size of the anomalous body was studied,and the relationship between the apparent resistivity anomalous position and the actual position of the anomalous body was analyzed; the detection sensitivity of this method to the geological bodies in front and below the survey line was established; a typical water-body detection model was established,simulation calculations were performed,and mapping based on the geomet ric intersection principle was used to explore the effects of typical water-body detection; Two typical unsuccessful exploration engineering examples were introduced,the detection results and the known ground ahead the water-rich condition of the layer were compared and explained. The results show that: anomalous body set on one si de of the point source cannot generate a sharp electric field change on the other side,and the"spherical shell"theory is inaccurate; the abnormal range of apparent resist ivity is much larger than the actual size of the abnormal body,and the abnormal position of the rate does not correspond to the actual position of the anomalous body; th e advanced detection results are mainly a reflection of the roadway floor rather than the geological situation in front of the roadway; the detection accuracy and resoluti on of the advanced detection method of the roadway working face of the direct current method are low,which is difficult to achieve in the result map. Overall,the theory and data processing and interpretation of direct current method used in roadway advanced detection are inaccurate.