Uma nova abordagem para análise de ruptura por galgamento de barragens homogêneas de solo compactado

• Ano de defesa: 2009
• Autor(a) principal: Aloysio Portugal Maia Saliba
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: galgamento de barragens; Ruptura; Barragens e açudes; Cisalhamento; Recursos hídricos Desenvolvimento; Engenharia sanitária
• Link de acesso: http://hdl.handle.net/1843/REPA-82YGMH

Dams have been considered as feasible alternatives to hydropower generation, tailings disposal etc in terms of costs, besides their inherent risks. In Brazil, dams are quite common. As the risks can be defined as the product of probability of failure and associated consequences, at the same probability level, reducing consequences also implies in lower risklevels. Erosion mechanisms observed on dam overtopping were studied in order to indentify the key aspects of risk reduction, with respect to hydraulic and geotechnical engineering. As identified on this research and from other authors, the compaction strongly interferes on soil erodibility. Dam-break models treat erosion from sediment transport theory point of view, that means assumptions of non cohesive properties and rough granulometry, if compared to finer soils as clays common in Brazil. In spite of sediment transport equations, this work uses the concept of erodibility, which considers materials erodibility, flow and geometry properties to each specific problem. The proposed methodology states that for every dam-break study, an erodibility test must be done and correlated to soil compaction, in order to define a erodibility function that can replace sediment transport equations on dam-break models. To assess soil compaction influence over a earthfill dam-break, geotechnical studies were carried out in soil samples obtained from Belo Horizonte, Minas Gerais, that were tested on aerosion apparatus designed by the author. Results indicate that there are significant differences on soil erodibility as soil compaction index raises from 95% to 100%. Influences of soil layers orientation relative to flow were also investigated on a flume, which results indicate that there are other processes interacting on dam breach erosion, besides flow erosion can be viewed as a trigger for them all. In order to assess the methodology applicability, one case study was done using Euclides da Cunha hydropower dam-break data, using the erodibility function obtained for Belo Horizonte soil, making an assumption that geotechnicalproperties could be considered the same. Results indicate differences by a factor of 2 to breach formation time and peak outflow 19% lower when compaction index raises from 95% to 100%.