Study of a water-retaining structure for the passage of sediments on reclamation canals

Abstract

Introduction. Been studied the passage of sediments through water retention structures (polygonal weirs) for angles of 30°, 45° and 60° for the side walls of the weir and a comparison of the results with each other and the classical weir (α= 90°) when laying the upper slope was 0; 1:1 and 2:1, according to the choice of the best model among the studied models that ensure maximum passage of sediment through the weir, protection of reclamation intakes from sediment while ensuring uninterrupted water consumption for irrigation systems and also improving irrigation water by passing sediment through the weir. Materials and methods. The passage of sediment through water retaining structures was studied in the Hydraulics Department laboratory of KubGAU on a glass tray 4.4 m long; 0.17 m wide; 0.3 m high. Polygonal and classical practical weir were made of gypsum material with angles 30°, 45°, 60° and 90° of the side walls of the weir. The upstream slope weir was 0; 1:1 and 2:1, and the laying of the lower slope was constant in all experiments – 1:2. Experiments were under the following conditions: The water flow rate Q was in the range of (0.58.10^-3 -9.94.10^-3 ) m³ /s, the diameter of the sediment particles was 0.1-0.25 mm, the pressure above the weir varied from h=1.3.10^-2 to 7.3.10^-2 m, and average water flow velocity were in the range from 0.041 to 0.409 m/s. Results and conclusion. Experimental studies of the passage of sediment through water retaining structure show that for all studied weirs, the average percentage of sand passing through a polygonal weir of a practical profile for the angles of the side walls α = 30°, 45° and 60° is 65.46%, 45.84% and 40.0% higher, respectively, compared with the classical one weir (α=90°). Based on experimental studies, it was proved that the maximum percentage of sand passing through a polygonal weir was 51.4% for a weir with a threshold height of 0.07 m, the angle of the side walls of the weir to its axis α = 30° and the laying of the upper slope 2:1.