Research on the detection of high-resistivity body by transient electromagnetic method

Although transient electromagnetic method is sensitive to low-resistivity body, abnormality of high resistivity has been observed in inflatable old mines or some water-filled old mines. Therefore, the key to the applicability of this method to detect old mines lies in that whether this method can indicate apparent abnormality of high-resistivity bodies. And results from simulating the underground transmission and reflection processes of transient electromagnetic field induced by step pulse with the help of FDTD method show that during the diffusion of electromagnetic field, distortion of contour line in electric field caused by high-resistivity is hardly to be noticed. However, by making comparison between contour lines, it can be seen that induced electro-dynamic force is high without high-resistivity body; while when there are high-resistivity bodies, eddy induced is small. There are still differences for the induced electro-dynamic force observed on ground surface with or without high-resistivity bodies. Therefore, transient electromagnetic method is applicable to be applied in detecting combusted area.