Flow through gabion weir

Código

I-EBHE0080

Autores

Ali Shariq, Mohammad Saud Afzal

Tema

WG 1.12: Development & application of river basin simulators

Resumo

Gabion weirs are one of the simplest porous weir-type hydraulic structures composed of wire mesh cages filled with rocks, stones, or boulders, usually provided across a river. Their eco-friendly nature, complex hydraulics, economic advantages, and greater stability compared to impermeable structures have gained attention from both practitioners and researchers. It is intended to manage water flow, reduce erosion, and strengthen streambeds and riverbanks. Many investigators made many experimental and numerical study for the hydraulics and turbulence characteristics of solid weirs. According to the literature, a few investigators have conducted experimental and numerical studies on gabion weirs for free-flow and submerged-flow conditions, while only two studies have examined flow through porous weirs under through-flow conditions. However, none of these studies developed empirical equations for predicting discharge. The aim of this study was to develop the dimensionless discharge relationship to evaluate the flow through rectangular broad-crested gabion weirs under through flow conditions. Laboratory experiments were conducted for discharge passes through the porous body of gabion weir under through flow conditions. All the experimental work was conducted at the Hydraulics and Water Resources Engineering Laboratory, Department of Civil Engineering, Indian Institute of Technology Kharagpur. The experimental setup had dimensions of 8.55 m in length, 0.42 m in depth, and 0.6 m in breadth. Experiments were carried out on gabion weirs with crest lengths (L) of 0.2 m, widths (B) of 0.6 m, and crest heights (P) of 0.3 m. The shape of boulders was almost spherical, and three different diameters of the boulders were used, ranging from 0.02 m to 0.065 m. Using Buckingham ? theorem, it was found that dimensionless discharge passes through the gabion weir is the function of the ratio of mean diameter of the boulder to the crest height of gabion weir, porosity and the ratio of difference between the upstream and downstream depth to length of gabion weir. The present study model was found to predict dimensionless discharge through the gabion weir within a maximum of ±15% error for nearly all datasets, which is considered satisfactorily. The present study model performance was assessed using parameter such as the coefficient of correlation (R), average percentage error (APE), standard deviation (STDV), and scattering index (SI). The qualitative evaluation of the model indicates a coefficient of correlation (R) of 0.80, with the low average percentage error (APE) at -0.90, standard deviation (STDV) of 5.43, and scattering index (SI) of 0.106. This study is very useful in managing the river and ocean system in the respect of environmental risk assessment of a water resources and flood mitigation project. The use of gabion weir in a river is advantageous in reducing the material cost and reducing the environmental hazards over other types of solid structures. The depth of scour at downstream of gabion weir is much smaller as compared to the solid structure which reduces the foundation depth and construction cost. The hydraulic designers and water resources engineers are interested to know the fundamental and structural performance of gabion weirs in all respects