Análise crítica do plano de instrumentação de UHE Risoleta Neves antes e após o acidente com a Barragem de Fundão em Mariana, MG

Abstract

Dam safety has become a critically relevant issue in Brazil, driven by recent large-scale disasters such as the failures of the Fundão (2015) and Brumadinho (2019) dams. This study examines the importance of civil structural monitoring instrumentation in risk prevention, focusing on a unique and technically complex case study: the Risoleta Neves Hydropower Plant. Following the collapse of the Fundão Dam, the Candonga HPP was directly impacted by the wave of tailings. Given the gap in the literature regarding the assessment of hydropower structures indirectly affected by mining dam failures, the main objective of this work was to conduct a critical analysis of the instrumentation plan of the Risoleta Neves HPP, comparing pre- and post-disaster scenarios. The adopted methodology consisted of an applied case study, with a qualitative, exploratory, and descriptive approach, based exclusively on documentary analysis of secondary data obtained from technical reports, scientific articles (such as Carvalho et al., 2023), Dam Safety Plans (DSP), and regulatory agency standards. It is emphasized that the instrumentation data analyzed, referring to piezometers and extensometers, were entirely extracted from these documentary sources and were not derived from direct measurements performed by the author. These data were organized into four distinct operational phases: Phase I (Initial Stabilization, 2004–2005), Phase II (Stable Commercial Operation, 2005–2015), Phase III (Failure Impact, 2015), and Phase IV (Sedimentation Period, 2015–2022). The results show that the original instrumentation system was robust, capturing the expected structural behavior during Phases I and II. In Phase III, the instruments demonstrated remarkable sensitivity, recording a reversal in kinematic trends and an immediate piezometric response to the abrupt reservoir drawdown, thereby validating the system’s functionality under an extreme loading event. In Phase IV, continuous monitoring proved essential for ensuring structural safety under the new sediment-induced loading regime, with readings consistently remaining below alert thresholds even during flood events. The study also mapped the significant expansion of the instrumentation system and concluded that these changes were technically justified and effective, enabling the safe management of an unprecedented scenario and the eventual refilling of the reservoir. This research demonstrates that structural monitoring instrumentation was the primary tool enabling the safe management of the dam, constituting a valuable learning case for dam engineering practice in Brazil.