Análises de risco aplicadas a barragens de terra e enrocamento: estudo de caso de barragens da CEMIG GT

Abstract

Dams are critical and essential elements in our infrastructure and, due to the recent accidents in the country (Brazil), there is an increasing demand from society to meet the risk imposed by these structures. This is underlined by the creation of the Dam Safety National Policy which enhances the relevance of the topic and fosters a culture of dam safety and risk management. In this context, technical risk analysis, widely adopted in other areas of knowledge, are important tools in a pressing approach towards risk oriented management. An overview of the risk analysis methods available in the literature with potential use in dams is presented, such as Risk Indexes, Location, Cause, Indicator Diagrams (LCI), Failure Mode and Effects Analysis (FMEA), Event Tree Analysis (ETA) and Fault Tree Analysis (FTA). The study aims to apply the methods essentially qualitative (Risk Indexes, LCI and FMEA), exposing their advantages and limitations and using them to rank a group of dams, as well as to perform detailed and systematic evaluation of structures identified as posing higher risk. The case study is performed on a group of earth and rockfill dams operated by the company Cemig Generation and Transmission S.A. (Cemig GT), supported by documentary research, deterioration database and field inspections. Despite the variety and subjectivity of qualitative methods, the results show that they tend to converge in terms of the risk-based classification of the dams. The implementation methodology indicates the feasibility of the evaluation in phases, including the preliminary portfolio risk analysis for the portfolio of dams, followed by formal and individual risk analysis for the most critical structures. The results confirm the applicability of the risk analysis techniques, thus contributing to the consolidation of this tool in the process of dam risk assessment.