Research and application of small-loop transient electromagnetic inversion method using improved FLCPSO-IFAH optimization algorithm

The small-loop transient electromagnetic (TEM) method for shallow surface engineering exploration is developing rapidly. However, the research on refined imaging methods of the small-loop TEM is slightly lagging behind, which seriously restricts its application effect in practical engineering and has become a key problem to be solved urgently. In this paper, the application effect of the improved nonlinear optimization algorithm in small-loop TEM method inversion was researched from the aspects of theory and application. Firstly, the operational principles of the PSO-IFAH algorithm were elucidated and its effectiveness in TEM inversion. However, the inversion results of the PSO-IFAH algorithm are easily affected by the search range of the initial model, resulting in reduced computational efficiency and inversion accuracy. Hence, a refined FLCPSO-IFAH inversion method was proposed for resolve the problem by the fast-imaging method and the linear iterative method constraints. The results show that the computation efficiency and accuracy of the FLCPSO-IFAH inversion method were increased by more than 60 % and 55 %. Case studies using known collapsed karst datasets revealed the proposed method's superior resolution and accuracy, particularly in highlighting subtle anomalous features. Finally, the FLCPSO-IFAH method is used for small-loop TEM data inversion. Combined with geological and borehole data, which accurately and effectively reflected the distribution of the surface electrical structure and the distribution of fault structure and dissolution zone were inferred. The research content provides a new and effective method for the refined data processing and interpretation of small-loop TEM.