Behavior of Gravity Dams Built on Sedimentary Rocks: Deformation Analysis of Dona Francisca HPP Foundation

This paper describes a case study whose goal is to present and analyze the main data related to the monitoring of foundation behavior of the Dona Francisca HPP (Hydro Power Plant) gravity dam whose foundation is essentially constituted by sedimentary rocks. The analysis of the foundation behavior was done in terms of deformations recorded during seventeen years of dam operation by multiple rod extensometers. Dona Francisca HPP dam was built in 2000, on the Jacuí River, in the central region of the Rio Grande do Sul State, Brazil. The geological and geotechnical conditions of the foundation are related to the Formação Caturrita rocks, made up mainly of sandstones and intercalated levels of siltstone and argillite. In the first five years of operation there was an intense stabilization process of the foundation rocky massif. After this period, it was verified the occurrence of stabilization at a lower rate. The deformation of the Dona Francisca HPP foundation is higher when compared with other larger dams, such as the Itaipu HPP dam.