Geophysical key indicators for tailings dam physical integrity monitoring - Brazil

Gilvan Sá, Marco Antonio Braga,Luiz Antonio Pinto e Almeida, Leonardo Santana de Oliveira Dias, Alan de Souza Cunha, Demetrius Cunha Gonçalves da Rocha and Ricardo Luiz Teixeira Telles

Abstract

The geotechnical monitoring of tailings dams combined with a suitable application of geophysical electrical methods can improve their structure evaluation, allowing several correlations between direct analyses and the resistivity anomaly pattern. Considering this synergy, twenty-three electrical resistivity sections (ERT) were acquired along the beach, abutments, and central part of a dam, totalizing 10,776 m of dataset. After the interpretation of each ERT section, comparing the anomaly ranges with the water level meters measurements, three resistivity zones were defined: Zones of low resistivity (<64 ohm-m), correlated to regions of high humidity; zones of high resistivity (> 357 ohm-m), interpreted as dry zones, and regions with intermediate resistivity values, located between these limits. The groundwater surface generated from the interpretation of the electrical resistivity dataset and the groundwater surface acquired from the water level gauges were almost coincident. On the right abutment, the conductive anomalies showed remarkable continuity, suggesting a high moisture content in this region with strong gradients (200 mV) directed towards the zone of low resistivity values identified in the sections. The analysis showed a robust correlation of the ERT data with localized physical geotechnical measurements, valuable for monitoring dam integrity, overseeing the structure's response to climate and operational changes, and ultimately mitigating the risks of failure. The results of this study support the adoption of a seasonal 4D electrical resistivity survey as an effective tool to monitor and manage surface and high humidity zones, key indicators of dam integrity throughout the entire structure.

Keywords:
dam monitoring; electrical methods; geotechnical measurements and mining