DESIGN CONDITIONS FOR MORNING-GLORY SPILLWAYS:APPLICATION TO POTRERILLOS DAM SPILLWAY

摘要

Design of morning-glory spillways has special features, because the hydraulic behavior of this structure is strongly related to the boundary topography, crest diameter, curve or bend downstream, spillway profile and the tunnel dimensions towards the outlet section. In the case of Potrerillos dam, located on Mendoza River, Argentina, a morning-glory spillway was selected. This spillway must be able to pass a design discharge of 1800 m3/s at flee surface, being characterized by a 31,76 m-crest diameter, 13.40 m-cross section diameter, a vertical 90° curve of 44.67 m-radio and a 400 m-length horseshoe cross section tunnel of 11.80 m-diameter. A special study was developed at National Institute of Water in order to analyze the hydraulic performance of the spillway. The physical model studies allowed determining a final location different from that considered in the project, optimizing the boundary conditions close to the spillways, modifying the number of piles on the crest and improving by these means the hydraulic performance of the whole structure, including flow characteristics inside tunnel. Final hydraulic design was compatible with structural design, allowing besides that a strong reduction of rock excavation.