Insights From Nuclear Magnetic Resonance Investigations in Tailings Storage Facilities

Nuclear magnetic resonance (NMR) measures interactions between atomic nuclei and magnetic fields. Recent advances in small-diameter probes now enable shallow subsurface investigations (<100 m), yet applications in tailings engineering remain limited. This study presents insights from NMR investigations at three tailings facilities with varying conditions. NMR responses are interpreted alongside CPTu data, seismic velocities, electrical resistivity, and laboratory results. Magnetic susceptibility (χ), mineralogy, and interbedding influence NMR performance. At Site 1, characterized by low χ (3.34×10⁻⁴), low Fe content (1.8%), and uniform stratigraphy, NMR-based volumetric water content (VWC) compares well with independent estimates. Accuracy decreases at Site 2 (moderate χ = 1.0×10⁻², high interbedding), and NMR data are unusable at Site 3 (high χ = 1.54×10⁻¹ and high Fe³). At Site 1, increasing signal-to-noise ratio narrows VWC estimates. At Sites 1 and 2, MMR is effective in identifying saturation transitions. Differences with other options (e.g., P-wave velocity) are discussed. NMR-derived VWC can also support the estimation of unit weight, void ratio, state parameter, relative density, and saturation. Error analysis indicates VWC errors <1.5-2.0% are needed for reliable void ratio estimates. Overall, findings highlight NMR’s potential for in situ tailings characterization, provided limitations from SNR, layering, and magnetic susceptibility are mitigated.