2.5-D Inversion of Advanced Detection Transient Electromagnetic Method in Full Space

The transient electromagnetic method (TEM) can be applied in detecting coal mining heading face with multiple angles. However, a 1-D inversion scheme cannot fit this kind of multi-angle data-receiving system well, nor reducing detection accuracy. Developing a 2.5-D inversion method is necessary for TEM multi-angle data. The expressions of the vertical and horizontal magnetic dipole source at any position in the layered medium are derived on the basis of the potential function and the boundary conditions of the electromagnetic field. Then, the electromagnetic field of the magnetic dipole source with multiple angles can be obtained through vector stacking. A low-resistance anomalous body above the roof in front of a roadway excavation was identified by applying a 2.5-D least square inversion method in mine TEM-advanced detection to verify the effectiveness of the inversion method. Moreover, the method was used to detect water inrush from one side of the roadway in a coal mine in Shandong Province, China. Furthermore, the inversion results were verified by the information of boreholes and excavation. The proposed 2.5-D inversion method has a higher interpretation accuracy and resolution than the 1-D inversion method of the model and the measured data.