1 Paper N0: II.10 Hydraulic Model Investigation of the Evacuation Structures of Dam St. Petka on Treska River

Abstract: Modern hydraulic engineering has been and remains to a large extent based on experimental investigations. Mathematical modeling techniques have progressed rapidly due to the advent of high-speed digital computers, enabling the equations of motion coupled with semi-empirical relationships to be solved for complex flow such as pipe network analysis, pressure transients in pipelines, unsteady flow in rivers, etc. There are many cases, particularly where localized flow patterns cannot be mathematically solved, when physical models are steel needed. The hydraulic model investigation of the evacuation structures of dam “St. PETKA ” on Treska River has been performed in Hydraulic laboratory at the Faculty of Civil Engineering in Skopje. The model was designed and constructed in scale 1:40. The evacuation structures that have been investigated are: diverse tunnel with intake structure, shaft spillway with spillway tunnel and output portal and bottom outlet with intake structure. The main objectives of the study are: to confirm the disposition and dimensions of the associate structures, to define their capacities, to define the flow patterns, to define the pressure distribution along the tunnels, to define the backwater influence of the downstream reservoir and to investigate the erosion processes in the river bed downstream. The investigations were performed on two stages: fixed-bed model and movable-bed model. On the fixed-bed model were investigated the capacities, pressure distribution and flow patterns in the structures. On the movable bed-model were investigated the erosion processes in the river bed downstream of the output structure. In this paper will be discussed the summary results that have been obtained within the study on physical model and the focus will be on the results on the shaft spillway