Induced polarization for landfill leakage imaging with interferences from metallic structures: modelling and field experiment

SUMMARY Metallic infrastructure, such as steel sheet situated within landfills, poses significant challenges to accurate tracking of leachate using induced polarization (IP) methods. The application of IP method is efficient to delineate leakage; however, the presence of metallic structures can cause an interference on the survey and generate high-chargeability anomalies as observed in field survey. To comprehensively validate the interference caused by steel sheets, both numerical and empirical field tests were conducted. As expected, both results demonstrate that interference diminishes as the distance between survey line and metallic structure increases. Additionally, at consistent intervals, the chargeability values inverted using integral chargeability (IC) exhibit a monotonic increase with depth. Moreover, the interference induced by metallic structures is also affected by the controlling factors (i.e. depth, width and thickness) of the structure alongside the intrinsic resistivity and chargeability. Strategic utilization of the size, chargeability and spatial positioning of metallic structures relative to survey lines can significantly enhance background polarization. This approach offers a promising framework for improving the spatial resolution of subsurface targets exhibiting low polarization effects. The optimization of survey line placement, which must consider the dimensions and electrical properties of metallic structures such as steel sheets, is essential for accurately characterizing landfill leachate using the IP method.