Electrical resistivity tomography applied to the geological-geotechnical characterization of the Serra Grande gold tailings dam (Crixás - GO, Brazil)

Tailings dams are essential structures for the safe management of mining waste. However, recent failures such as Mariana (2015) and Brumadinho (2019) have intensified concerns regarding their stability in Brazil. In response, characterization approaches integrating conventional geotechnical information with non-invasive geophysical methods have emerged as promising strategies to improve diagnostic capability and operational safety. This study presents an integrated methodology that combines electrical resistivity tomography (ERT) and geotechnical data to characterize the internal conditions of a gold tailings dam in Goiás, Brazil. Six 2D resistivity profiles were acquired and used to generate an interpolated 3D resistivity model, enabling: (i) quantification of characteristic resistivity ranges for different materials; (ii) construction of a 3D phreatic-surface model; and (iii) development of a conceptual relationship between pore pressure and electrical resistivity. The analysis allowed the definition of representative resistivity intervals for key materials, including saturated tailings (5–27 Ω·m), dry tailings (30–102 Ω·m), saturated saprolite (25–175 Ω·m), and dry saprolite (185–1924 Ω·m). The integrated interpretation enabled the identification of the internal drainage system, delineation of structural components, and recognition of zones associated with elevated pore-pressure conditions near the foundation, especially in low-permeability materials. The results emphasize the potential of ERT–geotechnical integration to improve hydrogeotechnical characterization and support the identification of potentially critical zones within the structure. This study demonstrates the applicability of integrating geophysical and geotechnical datasets for the characterization of gold tailings dams, contributing to improved safety practices and reducing environmental and operational risks.