Study on short offset transient electromagnetic detection technology for low-resistance electrical sources in deep mine

Deep mining in coal mines is a trend,but the accompanying complex water hazards pose a huge threat to safety.The aquifer in the super-thick conglomerate above the coal seam roof is characterized by shallow,deep and irregular development.The conventional ground transient electromagnetic detection depth is insufficient,and the volume effect of deep detection is large,and the low resistance shielding effect is obvious.In order to ensure safe mining of deep coal seams,the water content and water-rich range of the super-thick conglomerate above the coal seam roof were detected with high precision and high resolution.Based on the short offset transient electromagnetic method of electrical sources,the electrical properties were analyzed and the calculation expressions of the vertical magnetic field strength,apparent resistivity value and detection depth of the short-distance transient electromagnetic detection technology of the source were summarized.The research summarized the detection method of on-site multiple earthquakes and discussed the least squares based on the improved damping factor.It has been applied to the water-rich exploration of the thick conglomerate deep in a mining area in north China.The research results show that the short offset transient electromagnetic detection technology of electrical source increases the detection depth,realizes the effective detection of low-resistance water bearing anomalies with a depth of more than 1 000 m,reduces the volume effect of deep detection,and effectively suppress the influence of conductive shielding,and it obviously improves the detection accuracy of the deep thick conglomerate layer and the rich water range.After 38 iterations,the inversion error of the H-type theoretical model is 7×10-7,and the inversion error of the actual data is 0.05% after 50 iterations.According to the drilling verification of the low-resistivity anomaly area,the water output is consistent with the strong and medium water-bearing anomaly area,and the detection accuracy and resolution are significantly improved.This method provides effective geological technical data for safe mining of deep coal seam and has a high value of popularization and application.