Author(s): R. L. Branco; L. M. C. F. Fais; A. L. S. S. Matim; S. Malavasi; J. G. Dalfre Filho

Linked Author(s): Laura Maria Canno Ferreira Fais, José Gilberto Dalfré Filho

Keywords: Erosion; Cavitation; Water-solid; Experimental study; Dam safety

Abstract: The population growth requires improvements in water availability for consumption, food and energy. There are many challenges to achieve this. However, in many cases, one solution resolves all needs: reserving the water for supply, irrigation of crops and energy generation. In particular, the current demand for clean energy generation has encouraged some governments to invest in the construction of new hydropower plants. This scenario results in building a dam and its appurtenances. The concept of accumulating water for human use dates back to antiquity, but it was only during the 19th century that the technological development allowed the advent of hydropower plants. Since then, ongoing efforts on this field have developed technologies and the systematic construction of dams. More recently, there has been an increasing concern regarding the safety of dams. In Brazil, the safety legislation began to operate only in 2010. Malfunctioning of dams can lead to failure and even to catastrophic consequences. When an accident occurs, not only are the costs for repairing high, but it also compromises operation and the environment. A dam failure may be related to a poor performance of the spillway. Erosion is one of the main causes of spillways failure. In this sense, it is essential to characterize the composition and resistance of the concrete to be used in the spillway. Cavitation and water solid mixture are among the main causes of erosion that put spillways into risk. Cavitation is the formation of bubbles within the liquid, if the vapor pressure is reached. Once the pressure rises, the bubbles implode and eventually cause damage, noise, vibration and pressure fluctuation. Water solid mixture causes erosion by the impact of particles. The particles are carried in the flow, and it is especially important, because the damage is irreversible and progressive. The objective of this paper is to show the importance of testing concrete samples to erosion before using them in prototype. The concrete samples are submitted to erosion due to cavitation and water-solid mixture. The tests were performed at the Laboratory of Hydraulics and Fluid Mechanics at Unicamp, Brazil. The method for evaluating cavitation erosion resistance is based on the use of a high velocity cavitating jet. The other method, for evaluating water solid mixture erosion resistance, is based on the use of a mixing tank, where an impeller propels solid particles in the water over the sample. In both cases, the erosion resistance is associated with the mass loss of the sample through time. The results highlight the erosion that can occur in prototypes and the importance of testing concretes before construction or repairing of concrete spillways.

DOI: https://doi.org/10.15142/T3VW7Q

Year: 2018