Horizontal arranged long rectangular source TEM perspective for sensing hidden water-rich areas in an working face

With the realization of intelligent mines and ultrawide working faces, there are new challenges in current geophysical detection. To meet these challenges and achieve precise detection of water-rich areas within working faces, roofs and floors, we propose horizontally arranged long rectangular source transient electromagnetic (TEM) perspective detection technology. Compared to the traditional TEM based on mid to late stage data interpretation, the perspective technology proposed in this paper mainly focuses on early stage data interpretation. Particularly, a long rectangular loop is horizontally laid on one side of the working face roadway as the emission source, and transient induction signals are received on the opposite side of the roadway. By analyzing the signal characteristics, geological isomers inside the working face and floor are detected. First, the distribution pattern of TEM fields in the full space was obtained through theoretical analysis. Unlike ground TEM, the diffusion of TEM fields in full space is not affected by the ground-air boundary, and its spatiotemporal diffusion does not satisfy the smoke ring effect. Subsequently, through numerical simulation of different geoelectric models, the detection and resolution capabilities of the proposed TEM perspective method were studied. Compared with the traditional same-side transmission and reception mode, the early data of the perspective observation mode are mainly affected by transient changes in the primary magnetic field, which has high resolution. Late stage data are affected by the inflection points of positive and negative data, making it difficult to accurately obtain abnormal body information. Finally, an on-site experiment was conducted in a coal mine in Henan, China. The experimental data characteristics were highly consistent with the synthesized data, verifying the method's feasibility. Additionally, the result accuracy was further verified by on-site drilling data. The proposed method not only improves the accuracy of TEM detection in mines but also enriches the detection environment of TEM methods.