Abnormal response characteristic simulation during transient electromagnetic detection in mine borehole

Conventional mine transient electromagnetic advance detection method is greatly influenced by the condition outside of the mine, which leads to the inaccurate location in anomalous body detection. In order to solve this problem, an advance detection method for measuring the three-component signals of the transient electromagnetic field in the down-hole borehole was proposed to carry out numerical simulation for the abnormal response characteristics from the different locations of the plane where the receiving coil is located and the different orientations of the anomalous body. The principle of borehole transient electromagnetic detection was analyzed, and the test design and construction design for the borehole transmitting coil and receiving coil were carried out. The uniform full-space model, uniform full-space anomalous body model, and the three-component abnormal field response characteristics when the anomalous body is located at different orientations of the borehole, were systematically analyzed. When the low-resistivity anomalous body was perpendicular to the coil, the abnormal response of components X, Y and Z was the maximum. As the low-resistivity anomalous body was gradually parallel to the normal direction of the receiving coil, the abnormal response was gradually reduced. When the low-resistivity anomalous body was completely parallel to the normal direction of the receiving coil, the abnormal response of the components X, Y and Z was minimum. Through this method, the orientation of the borehole where the anomalous body is located can be determined based on the principle that the abnormal field three-component combination forms are different for different quadrant locations in the radial direction of the borehole. In the coordinate system, where the drilling direction of the borehole was the positive direction of Z axis, the right direction of the plane where the borehole collar was located was the positive direction of X axis, and the downward direction was the positive direction of Y axis. All the abnormal response forms of the borehole transient electromagnetic horizontal component were either "approximately sine curves" or "approximately inverted sine curves". The quadrant where the anomalous body near the borehole can be determined through the form of combinations. Through such regularity, the spatial location and the occurrence status of the anomalous body under 3D spatial conditions. Through the analysis of the abnormal response characteristics during borehole transient electromagnetic advance detection, the theoretical data supporting the borehole transient electromagnetic advance detection can be provided.