2. 5D inversion of borehole transient electromagnetic method with scanning detection based on RCQPSO-LMO combined algorithm

Boreholes logging methods are used in underground mining to detect geological structures and water-bearing bodies to guide underground excavation engineering. TEM scanning detection methods is an in-hole logging method intended for fine detection of geological linked to electrical conductivity contrast proximal to the borehole wall. This paper provides a 2. 5D inversion and interpretation method for an in-hole TEM scanning detection method. We find that random inversion algorithms are relatively time consuming and tend to fall into the local optimal solution while the deterministic inversion algorithms rely on the initial model. We develop a combined strategy with a quantum particle swarm optimization (QPSO) algorithm that randomly searchers for the optimal initial model. Here the Levenberg-Marquarat (LM) method is used to solve the objective function of Occam inversion and the RCQPSO-LMO combined algorithm was deployed for 2. 5D inversion. The combined and single algorithm is comparing, and it is verified that the combined algorithm yields a more accurate inversion outcome. Further, we test our 2. 5D inversion strategy with scanning detection under shielding conditions. That is, numerical tests are completed with and without shielding. By setting shielding coefficients to partially suppress the non-detection direction signal, the inversion outcome of the scanning methods can be improved. The inversion and imaging of the non-detection direction signal in the radial scanning detection is better resolved. Finally, three groups of theoretical models were established for 2. 5D inversion of the combined algorithm. The inversion results show that the combined algorithm is in good agreement with the theoretical model, and the inversion accuracy of a low-resistance anomaly is highly reasonable. We have demonstrated through numerical modelling that the combined algorithm has high inversion accuracy and resolution for low-resistance anomalies proximal to the borehole wall.