Investigation of the Effect of Downstream Slope and Rockfill Materials on Flow Regimes over Gabion Stepped Weirs
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Department of Civil Engineering, Faculty of Engineering, University of Babylon, Hillah, Babylon 51001, Iraq
Department of Environment Engineering, Faculty of Engineering, University of Babylon, Hillah, Babylon 51001, Iraq
School of Engineering, Faculty of Science Engineering & Built Environment, Deakin University, 75 Pigdons Road, Waurn Ponds, VIC 3220, Australia
Department of Environment Engineering, College of Engineering, University of Babylon, Babylon 51001, Iraq
Research and Studies Unit, Al-Mustaqbal University College, 51001, Babylon, Iraq
Building and Construction Techniques Engineering, Al-Mustaqbal University College, 51001, Babylon, Iraq
Department of Civil Environmental and Natural Resources Engineering, Lulea University of Technology, SE-971 87 Lulea
Submission date: 2022-11-07
Final revision date: 2023-01-09
Acceptance date: 2023-02-25
Online publication date: 2023-06-30
Publication date: 2023-07-21
Corresponding author
Nadhir Al-Ansari   

Lulea University of Technology, Dept. Civil, Environmental and natural Resources E, 971 87, Lulea, Sweden
Pol. J. Environ. Stud. 2023;32(4):3481-3490
It is important to determine the limits of flow regimes in the design of stepped weirs because of the hydraulic performance of each regime. The present study investigates the effect of downstream slope and rock fill materials on flow regimes in gabion stepped weirs. Nine physical models of gabion weirs were used in the experiments. The models’ downstream slopes ranged from 1:05 to 1:4 V:H. In addition, two types of rockfill materials: crushed stone of 0.42 porosity and rounded gravel of 0.38 porosity were used to study the effect of rockfill materials on flow regimes. The nominal size of the crushed stone was (37.5 mm - 13.2 mm) D50 = 23 mm and the nominal size of the rounded gravel was (26.5 mm - 13.2 mm) D50 = 16 mm. Each model has been tested with ten runs for discharge per unit width ranging (from 0.006 to 0.105 m3/sec. m) to cover all flow conditions and flow regimes. The onset of each flow regime for all physical models has been observed. The experimental data of the gabion stepped weirs have been used to develop equations to estimate the onset of each flow regime. The coefficient of correlation (R) of the developed equations ranged between 0.95 to 0.97. The results indicated on the steeper downstream slope models (1:0.5, 1:0.83), there is interference between the nappe and transition flow regimes. The nappe flow regime has not appeared on all steps at the same time. Moreover, the shape and size of the rockfill materials have an insignificant effect on flow regimes, especially at a high flow rate.
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