Water conveyance structure2/17/2024 The main objective of the study is to contribute to the field’s understanding of how to best design and manage canal coverage structures to reach an optimum performance. The investigation, conducted via experimental and numerical modelling, measures the changes in water levels and velocities due to blockage. Addressing these gaps, this study aims to evaluate the effects of blockage at the inlet of variously shaped canal coverage structures on their hydraulic parameters. Moreover, most studies have focused on pipe and box-shaped structures, leaving other shapes less explored. The effects of inlet blockage on open channel performance still require more investigation. While substantial work has been done in this field, gaps still persist. In relation to canal coverage structures, studies have examined the effects of different blockage ratios and blockage at the inlet of coverage structures. Other research has investigated the effects of blockage on flood behaviour, culvert scour depth, and turbulent flow conditions. Studies also highlighted the risk of embankment overtopping and failure due to culvert blockage. found that smaller culverts (with an opening less than six meters measured diagonally) are more susceptible to blockage, independent of other variables such as material type or land use. Understanding the impact of blockage, researchers have explored how various factors affect the risk and repercussions of this issue. El Baradei and Alsadeq suggest that the covered area should not exceed 32.8% of the total canal surface to maintain optimal DO and BOD levels. However, while a coverage structure is effective in quantity preservation, there are concerns about its impact on water quality. In this study, the phrase “canal coverage structure” is employed to encompass a wider array of constructions, extending beyond culverts to include diverse structural designs utilized to cover canals (Fig. The solution lies in canal coverage structures, which are culvert-like constructions that reduce streambed recharge and evaporation losses. In addition to human factors, climate changes and global warming contribute to water losses from irrigation canals due to seepage and evaporation. Irrigation canals' function can be compromised when they pass through residential areas, with the inappropriate disposal of waste leading to decreased efficiency and water quality. Central to these systems are the canals that serve as primary conduits for water conveyance, their performance is significantly influenced by their accompanying infrastructure, including weirs, culverts, and bridges. The efficient operation of irrigation systems is critical to sustaining agricultural productivity, particularly in the face of the current water scarcity and increasing population pressures. The findings from this study provide valuable insights for engineers and decision-makers involved in canal management and infrastructure planning. Considering the construction complexities associated with the pipe arch, the rectangular box is recommended as the most practical and efficient option for canal coverage structure design. Among the shapes studied, the pipe arch had the best performance in terms of head loss reduction, while a rectangular box with a height to width ratio of 2:3 was found to be a close second. The extent of this reduction varied with different coverage shapes, and the sensitivity to blockage was found to be the highest in the square box section, followed by the pipe section at the same design Froude number.Ī crucial threshold was identified at a blockage ratio of 30% where the performance of coverage structures started to decline sharply, indicating a key maintenance point. The study demonstrated that blockage in a canal coverage structure and its extent significantly impairs the structure’s hydraulic performance, leading to an increased head loss ratio and a reduced velocity ratio. An experimental setup was used in the study along with the HEC-RAS 1D numerical model, which was evaluated through a series of comparative tests. Seven coverage cross-section shapes, namely the square box, pipe, pipe arch, ellipse, arch, conspan arch, and rectangular box, were studied in combination with 10 different Froude numbers and 10 different blockage ratios. This study investigates the effects of blockage in canal coverage structures, focusing on various cross-sectional shapes and blockage ratios. The difficulty of removing wastes from closed canals further exaggerates the problem. Despite the benefits of canal coverage structures, they may turn out to be a significant reason of decreasing canals conveyance efficiency if they are subject to blockage.
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