Technique of Detecting Small Structure with Electromagnetic Wave CT in Pressure Zone of Fully Mechanized Mining Face

Through the electromagnetic wave CT detection test in the local pressurized area of 61114 fully mechanized mining face in Dafanpu Coal Mine of Ordos, it has carried out systematic research on consistency test, optimization of parameters such as frequency, interference test of iron tools, comparison of inversion methods, analysis of test results, comprehensive inference and verification, and optimized the technical system of test, construction, treatment and interpretation for fine detection of small structures in Ordos area. The results show that in the case of coal seam pressure and small structure development in Ordos area, the comprehensive detection technology for detecting structure by radio wave perspective detection and detecting water bodies by transient electromagnetic method could effectively predict the potential pressure water inrush point. During the construction process for the large length working face of Ordos, the transmission frequency should be 365 kHz or 188 kHz; the receiving coil should be far away from the iron, the horizontal distance should be more than 0.6 m, the vertical distance should be more than 0.4 m, the power in the construction area should be cut off as far as possible, the space between the coil and the coal wall should not be too large, and it should be close to the coal wall. The inversion calculation method should be optimized to form a reliable result map after comprehensive comparison of all kinds of result maps, so as to improve the detection accuracy and realize fine treatment and interpretation.