Segurança de barragens de terra: simulação do estabelecimento de níveis de controle piezométricos para a barragem Cana Brava, no Ceará

Abstract

Dams are structures of immense relevance to people and public entities because they provide several resources that are essential to human development, such as water supply, irrigation, and electricity. Furthermore, dams are enterprises that require monitoring due to the possibility of failures or ruptures, which is an enormous risk to human lives, the environment, and the economy. In the last years, following big dam bursts in the country, Brazilian legislation has been improving and becoming more strict concerning the entrepreneurs’ responsibilities and regulatory affairs. The primary goal of this presente work is to define the control levels for the piezometers in Cana Brava earth dam, localized in the city of Brejo Santo, in the state of Ceará. In order to do so, a theoretical foundation about the purposes and operation of the most used instruments of auscultation in Brazilian dams was carried out, a thorough understanding of the flow behavior and the pore pressure in earth dams was performed, and it was addressed how this subject fits in the Dam Safety Act and the demands of The National Water and Sanitation Agency (ANA) as a supervisory organ. Based on the enterprises' projects of this case study and their measurement reading of instruments, the definition of the reference range was accomplished through mathematical models grounded in two different scenarios: in the first one, the behavior of the dam is functioning as established on the project. The second was a hypothetical setting, named critic, in which the dam drainage system is unworkable. Therefore, it was obtained the pore pressure distinctions measured by piezometers in each scenario, and it was settled the percent relative range of the value of that difference in alert, attention, or emergency circumstances taking into account the piezometers studied. Hence, a chart containing the three reference values has been created, which can be utilized in the analytical reports of Dam Monitoring Instrumentation to improve the watching of measurement reading of piezometers. Moreover, it was possible to identify the correct operation of the dam drainage system by comparing the results obtained by the numerical analysis and the current measurement values of the instruments.