Technical University of Cartagena Research. Study Cases: Paute Cardenillo and Toachi Dams

Abstract

The increasing of the magnitude of design floods has prompted the re-evaluations of spillway capacity and theoperational scenarios for large dams throughout the world. Current capacity of many spillways is inadequate anddams might be overtopped during extreme events. New loading for the dam and questions about erosion and scourdownstream from the dam are necessary. In this way we need to estimate the hydrodynamic actions on the dambottom or the basin where the jet discharges, as a function of the characteristics of the jet. So the pressure andvelocity distributions of the flow in the plunge pool must be estimated to evaluate potential scour that mightdestabilize the dam. The high turbulence and aeration phenomena that appear in falling jets and dissipation basinsmake it difficult to carry out studies based only on classical methodologies. This work addresses overtopping flows,and compares numerical results against our own experiments. Instantaneous pressures, velocities and airentrainment were obtained with the use of piezoresistive transducers, Acoustic Doppler Velocimeter and opticalfiber, respectively. Mean velocity field and turbulence kinetic energy profiles were determined. To identify the levelof reliability of models, numerical simulations were carried out by using the “homogeneous” model of ANSYS CFX,together with different turbulence closures.In this paper we also present two Study Cases: Paute - Cardenillo (arch dam of 135 m height) and Toachi (gravitydam of 59 m height). To evaluate the stability and safety of the structures, it is necessary to ascertain the shape anddimensions of the scour generated downstream from the dams. We studied the scour, due to the operation of the freesurface spillway and half-height outlets (Paute-Carenillo dam) with three complementary procedures: empiricalformulae obtained in models and prototypes, semi-empirical methodology based on pressure fluctuations-erodibilityindex and computational fluid dynamics simulations (Flow-3D). A pre-excavated basin is proposed in PauteCardenillol dam and the velocities and pressures are analyzed. In the case the of the Toachi dam sky jump, inaddition to the three previous procedures, a physical model 1:50 scale was carried out. The results demonstratedthe suitability of combining different methodologies to achieve an adequate resolution of this complex phenomenon.