Accurate Modeling Approach and Uncertainty Quantification for TEM Weak-Coupling Coil: A Case Study on Bucking Coil

The small-loop transient electromagnetic (TEM) method can effectively investigate urban underground space. However, due to the severe mutual induction between the transmitting and receiving coils, the secondary field signal containing underground shallow information is contaminated by the primary field interference. Weak-coupling coils can reduce the effect of mutual induction, but the residual mutual induction (RMI) still affects the early secondary field response, resulting in the loss of shallow information. In this article, we take the bucking coil as a case to refine the model of the small-loop TEM weak-coupling coil and propose an RMI uncertainty quantification method based on sparse polynomial chaos expansion to guide the coil design. The simulation results show that compared with the conventional design method, considering the refined structure of the wire layer overlap can more effectively reduce RMI in the presence of processing and installation errors. The experimental results show that the new structure proposed can improve the ability to distinguish the anomalous body in the shallow space of the urban underground space and has strong practicality.