Avaliação dos Níveis Piezométricos Críticos de uma Barragem de Terra: Um Estudo de Caso da Barragem Jaburu I

Abstract

Dams are structures whose main purpose is the storage of water or accumulation of tailings and debris. However, as much as these structures are designed to benefit the population, the opposite occurs, in some cases, such as in failure situations. In this context, the uncontrolled water flow through the dam can be one of factors that can potentiate a possible failure, through the sliding of slope downstream of massif. With this in mind, different types of instruments were created, such as piezometers, which made it possible monitor the water flow through the dam. Allied to this, some types of internal filters were also created, in order to control the water flow inside the massif, however, these filters can be subject to a clogging process throughout their useful life, becoming inefficient, presenting risks to the structure. Because of this, stability studies become more necessary to ensure the dam’s preservation, however, frequent studies can lead to higher operational costs to manager agencies. With this in mind, the present study proposes a methodology of “critical piezometers levels”, in which the readings of piezometers installed in an earth dam and numerical modeling are used to determine the critical porepressures of the dam, which represent a coefficient of safety equal to the minimum recommended value, with a higher speed and with less operating costs, using Jaburu I Dam as a case study. For this, computational modeling of the dam’s maximum section was carried out, using GeoStudio 2021.4 software, calibrating the model from the real readings of the piezometers of Jaburu I Dam, between 1999 and 2013, provided by Companhia de Gestão dos Recursos Hídricos, so that the model represents consistent results with those verified in the piezometers. With this, stability studies of the downstream slope were carried out for different situations of dam’s internal filter clogging, obtaining the coefficient of safety of the dam for each scenario. Through this, it was possible to perform the correlation between the dam’s factors of safety and the porepressures, obtaining equations that describe this behavior, thus establishing the dam’s critical piezometers levels. Based on this, a retro-analysis of the dam's stability was carried out, obtaining, in the worst scenario, a factor of safety of 1.36, below the minimum recommended value for the situation under study, which was also observed by Souza et al. (2005). Thus, it was found that the methodology of critical piezometric levels tends to obtain satisfactory results.