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Gholamreza Moharrami - One of the best experts on this subject based on the ideXlab platform.
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Performance of Cutoff Walls Under Hydraulic Structures Against Uplift Pressure and Piping Phenomenon
Geotechnical and Geological Engineering, 2015Co-Authors: Abdolreza Moharrami, Gholam Moradi, Masoud Hajialilue Bonab, Javad Katebi, Gholamreza MoharramiAbstract:This study is focused on a numerical method to investigate the performance of cutoff walls system against uplift pressure and piping phenomenon. The parametric study has been conducted on the variation of cutoff wall parameters such as inclination angle of one cutoff wall in upstream and downstream side of the Hydraulic Structure, their length in upstream side, their spacing and number of cutoff walls under Hydraulic Structure. The results showed that using inclined upstream cutoff wall θ = 70° and θ = 90° was beneficial in increasing the safety the Hydraulic Structure against piping phenomenon and uplift pressure, respectively. Using downstream cutoff wall with any inclination angle decreased the safety against uplift pressure, and the best inclination angle of the cutoff wall at the toe of the Hydraulic Structure in increasing the safety against piping phenomenon was θ = 130°. Increasing the length of the upstream cutoff wall increased the safety against uplift pressure and piping phenomenon. The use of the larger spacing between two vertical cutoff walls decreased the safety against uplift pressure and increased the safety against piping phenomenon. Finally, the best number of cutoff walls in increasing the safety against uplift pressure was three and also increasing the number of cutoff walls increased the safety against piping phenomenon.
Bartlomiej Wyzga - One of the best experts on this subject based on the ideXlab platform.
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sediment transport processes related to the operation of a rapid Hydraulic Structure boulder ramp in a mountain stream channel a polish carpathian example
2015Co-Authors: Karol Plesinski, Artur Radeckipawlik, Bartlomiej WyzgaAbstract:Rapid Hydraulic Structures—RHS—(called also boulder ramps) are modern, environment-friendly grade-control Structures which mimic natural riffles and do not disturb longitudinal continuity of the stream for fish and benthic invertebrates. Due to the reduction of Hydraulic gradient and backwater effect, such Hydraulic Structures change the pattern of sediment transport and deposition in the channel, facilitating persistence of alluvial streambed and the formation of gravel bars upstream and downstream of the Structures. This is of key importance for preserving habitats for benthic invertebrates and the spawning ground of lithophilic fish if a stream has to be channelized. At the same time, properly designed rapid Hydraulic Structures must allow efficient transfer of sediment flux through their apron, helping to clean the Structures of gravel and preventing their clogging. This study deals with observations and modeling of sediment transport in the vicinity of a rapid Hydraulic Structure in a mountainous gravel-bed channel. The study aims to: (i) show the effects of RHS on sediment transported along a stream channel, and (ii) to evaluate the performance of CCHE2D model in predicting sediment phenomena along the stream with rapid Hydraulic Structures. The studied Structure is located in Porebianka Stream draining a flysch catchment in the Polish Carpathians. We measured and calculated Hydraulic parameters characterizing the flow on and in the vicinity of the Structure, such as velocity, dynamic velocity, shear stress, Froude number, Reynolds number and friction coefficient. The knowledge of those parameters allowed us, at the same time, to calculate sediment transport in the region of the Structure using BAGS model for the Parker transport formula and parallel modeled the sediment transport with the CCHE2D model. The results show how the Hydraulic Structure (enabling the migration of fish and benthic invertebrates), operates in terms of sediment transport processes (basically, giving the answer to the question: what is the influence of RHS on sediment transport) which form the channel morphology in its vicinity. In that context the CCHE2D model is discussed with its advantages and impediments.
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sediment transport processes related to the operation of a rapid Hydraulic Structure boulder ramp in a mountain stream channel a polish carpathian example
2015Co-Authors: Karol Plesinski, Artur Radeckipawlik, Bartlomiej WyzgaAbstract:Rapid Hydraulic Structures—RHS—(called also boulder ramps) are modern, environment-friendly grade-control Structures which mimic natural riffles and do not disturb longitudinal continuity of the stream for fish and benthic invertebrates. Due to the reduction of Hydraulic gradient and backwater effect, such Hydraulic Structures change the pattern of sediment transport and deposition in the channel, facilitating persistence of alluvial streambed and the formation of gravel bars upstream and downstream of the Structures. This is of key importance for preserving habitats for benthic invertebrates and the spawning ground of lithophilic fish if a stream has to be channelized. At the same time, properly designed rapid Hydraulic Structures must allow efficient transfer of sediment flux through their apron, helping to clean the Structures of gravel and preventing their clogging. This study deals with observations and modeling of sediment transport in the vicinity of a rapid Hydraulic Structure in a mountainous gravel-bed channel. The study aims to: (i) show the effects of RHS on sediment transported along a stream channel, and (ii) to evaluate the performance of CCHE2D model in predicting sediment phenomena along the stream with rapid Hydraulic Structures. The studied Structure is located in Porebianka Stream draining a flysch catchment in the Polish Carpathians. We measured and calculated Hydraulic parameters characterizing the flow on and in the vicinity of the Structure, such as velocity, dynamic velocity, shear stress, Froude number, Reynolds number and friction coefficient. The knowledge of those parameters allowed us, at the same time, to calculate sediment transport in the region of the Structure using BAGS model for the Parker transport formula and parallel modeled the sediment transport with the CCHE2D model. The results show how the Hydraulic Structure (enabling the migration of fish and benthic invertebrates), operates in terms of sediment transport processes (basically, giving the answer to the question: what is the influence of RHS on sediment transport) which form the channel morphology in its vicinity. In that context the CCHE2D model is discussed with its advantages and impediments.
Artur Radeckipawlik - One of the best experts on this subject based on the ideXlab platform.
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sediment transport processes related to the operation of a rapid Hydraulic Structure boulder ramp in a mountain stream channel a polish carpathian example
2015Co-Authors: Karol Plesinski, Artur Radeckipawlik, Bartlomiej WyzgaAbstract:Rapid Hydraulic Structures—RHS—(called also boulder ramps) are modern, environment-friendly grade-control Structures which mimic natural riffles and do not disturb longitudinal continuity of the stream for fish and benthic invertebrates. Due to the reduction of Hydraulic gradient and backwater effect, such Hydraulic Structures change the pattern of sediment transport and deposition in the channel, facilitating persistence of alluvial streambed and the formation of gravel bars upstream and downstream of the Structures. This is of key importance for preserving habitats for benthic invertebrates and the spawning ground of lithophilic fish if a stream has to be channelized. At the same time, properly designed rapid Hydraulic Structures must allow efficient transfer of sediment flux through their apron, helping to clean the Structures of gravel and preventing their clogging. This study deals with observations and modeling of sediment transport in the vicinity of a rapid Hydraulic Structure in a mountainous gravel-bed channel. The study aims to: (i) show the effects of RHS on sediment transported along a stream channel, and (ii) to evaluate the performance of CCHE2D model in predicting sediment phenomena along the stream with rapid Hydraulic Structures. The studied Structure is located in Porebianka Stream draining a flysch catchment in the Polish Carpathians. We measured and calculated Hydraulic parameters characterizing the flow on and in the vicinity of the Structure, such as velocity, dynamic velocity, shear stress, Froude number, Reynolds number and friction coefficient. The knowledge of those parameters allowed us, at the same time, to calculate sediment transport in the region of the Structure using BAGS model for the Parker transport formula and parallel modeled the sediment transport with the CCHE2D model. The results show how the Hydraulic Structure (enabling the migration of fish and benthic invertebrates), operates in terms of sediment transport processes (basically, giving the answer to the question: what is the influence of RHS on sediment transport) which form the channel morphology in its vicinity. In that context the CCHE2D model is discussed with its advantages and impediments.
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sediment transport processes related to the operation of a rapid Hydraulic Structure boulder ramp in a mountain stream channel a polish carpathian example
2015Co-Authors: Karol Plesinski, Artur Radeckipawlik, Bartlomiej WyzgaAbstract:Rapid Hydraulic Structures—RHS—(called also boulder ramps) are modern, environment-friendly grade-control Structures which mimic natural riffles and do not disturb longitudinal continuity of the stream for fish and benthic invertebrates. Due to the reduction of Hydraulic gradient and backwater effect, such Hydraulic Structures change the pattern of sediment transport and deposition in the channel, facilitating persistence of alluvial streambed and the formation of gravel bars upstream and downstream of the Structures. This is of key importance for preserving habitats for benthic invertebrates and the spawning ground of lithophilic fish if a stream has to be channelized. At the same time, properly designed rapid Hydraulic Structures must allow efficient transfer of sediment flux through their apron, helping to clean the Structures of gravel and preventing their clogging. This study deals with observations and modeling of sediment transport in the vicinity of a rapid Hydraulic Structure in a mountainous gravel-bed channel. The study aims to: (i) show the effects of RHS on sediment transported along a stream channel, and (ii) to evaluate the performance of CCHE2D model in predicting sediment phenomena along the stream with rapid Hydraulic Structures. The studied Structure is located in Porebianka Stream draining a flysch catchment in the Polish Carpathians. We measured and calculated Hydraulic parameters characterizing the flow on and in the vicinity of the Structure, such as velocity, dynamic velocity, shear stress, Froude number, Reynolds number and friction coefficient. The knowledge of those parameters allowed us, at the same time, to calculate sediment transport in the region of the Structure using BAGS model for the Parker transport formula and parallel modeled the sediment transport with the CCHE2D model. The results show how the Hydraulic Structure (enabling the migration of fish and benthic invertebrates), operates in terms of sediment transport processes (basically, giving the answer to the question: what is the influence of RHS on sediment transport) which form the channel morphology in its vicinity. In that context the CCHE2D model is discussed with its advantages and impediments.
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on using artificial rapid Hydraulic Structures rhs within mountain stream channels some exploitation and Hydraulic problems
2013Co-Authors: Artur RadeckipawlikAbstract:The chapter describes rapid Hydraulic Structure (RHS) with increased roughness: one of the technical solutions intended to maintain river and stream beds in a good condition and at the same time ensure the development of a braided channel and contribute to the regeneration of channel bar Structures, creating suitable living conditions for macrobenthos, and enabling unconstrained fish migration without additional fish passes. The chapter also discusses the problem of rebuilding the existing water straight drop Structure in Brenna on the Brennica River (Polish Carpathians) which was changed into the rapid Hydraulic Structure. The technical project was set up in 1988 and finished in the same year. The Structure was rebuilt in the field in early autumn 1990. The author of the chapter was a co-designer of the Hydraulic Structure.
Abdolreza Moharrami - One of the best experts on this subject based on the ideXlab platform.
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Performance of Cutoff Walls Under Hydraulic Structures Against Uplift Pressure and Piping Phenomenon
Geotechnical and Geological Engineering, 2015Co-Authors: Abdolreza Moharrami, Gholam Moradi, Masoud Hajialilue Bonab, Javad Katebi, Gholamreza MoharramiAbstract:This study is focused on a numerical method to investigate the performance of cutoff walls system against uplift pressure and piping phenomenon. The parametric study has been conducted on the variation of cutoff wall parameters such as inclination angle of one cutoff wall in upstream and downstream side of the Hydraulic Structure, their length in upstream side, their spacing and number of cutoff walls under Hydraulic Structure. The results showed that using inclined upstream cutoff wall θ = 70° and θ = 90° was beneficial in increasing the safety the Hydraulic Structure against piping phenomenon and uplift pressure, respectively. Using downstream cutoff wall with any inclination angle decreased the safety against uplift pressure, and the best inclination angle of the cutoff wall at the toe of the Hydraulic Structure in increasing the safety against piping phenomenon was θ = 130°. Increasing the length of the upstream cutoff wall increased the safety against uplift pressure and piping phenomenon. The use of the larger spacing between two vertical cutoff walls decreased the safety against uplift pressure and increased the safety against piping phenomenon. Finally, the best number of cutoff walls in increasing the safety against uplift pressure was three and also increasing the number of cutoff walls increased the safety against piping phenomenon.
Lodomez Maurine - One of the best experts on this subject based on the ideXlab platform.
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Experimental Study of Nappe Oscillations on Free Overfall Structures
Université de Liège Liège Belgique, 2019Co-Authors: Lodomez MaurineAbstract:Free-overfall Structures such as weirs and crest gates are commonly used as control Structures for a variety of applications including irrigation, water treatmentand dam safety. The gravity-driven free falling jet on the downstream side of these Structures, called the nappe, may display a variety of behaviors and instabilities among which, under relatively low heads/discharges, nappe oscillations, also known as nappe vibrations. This oscillating phenomenon is characterized by oscillations of the thin flow nappe cascading downstream of the crest and results in a significant disturbing noise production that increases negatively the environmental and societal impacts of the Hydraulic Structure. Given the lack of quantitative information reported in literature and the inchoate understanding of the dominant processes underpinning nappe oscillations occurrence and development, the global objective of this PhD thesis was to improve the knowledge of the nappe oscillation phenomenon. To that end, experimental modelling was seen as the best way to analyse the problem. First, a prototype scale model of a linear weir has been specifically designed and made flexible with respect to the main parameters of the weir. Then, two original characterization methods of the nappe oscillations properties have been developed based on the distinct audio and visual traits of the phenomenon. The application of these methods allowed the determination of the occurrence and development of the oscillations and their associated frequencies. Both were used systematically to assess the influence of various Hydraulic and geometric parameters on the nappe oscillation phenomenon. Secondly, given the importance of scale physical modelling for Hydraulic Structure design, the possible scale effects affecting nappe oscillation were studied by considering a 1:3 scale model of the aforementioned prototype scale facility. The operation of this second model showed that nappe oscillations cannot be scaled according to the traditional similitude for weirs (Froude similitude). Instead, they always occur within the same unit discharge range independent of size scale, although they are prone to hysteretic behaviour and are less stable over time for smaller weir dimensions. Third, considering the data collected from the study of 52 geometric configurations and the expertise gained from hours of nappe oscillation observations and analysis, necessary conditions for nappe oscillation occurrence have been defined. Along with geometrical criteria regarding the fall height and width of the Structure, these conditions, although not sufficient, allow to predict the occurrence of the oscillation in many cases. Finally, original mitigation techniques have been developed with the help of practicing engineers and contractors. Identified with respect to constructability, durability, performance and maintenance, these solutions were tested and optimized regarding disturbing noise reduction without impacting the Hydraulic efficiency of the Structure. Beside these extensive experimental works, in-situ measurements at two Belgian dams proved the applicability and robustness of the measurement methodologies developed in the framework of this thesis and the utility of the results to solve real world problems
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Nappe oscillations on free-overfall Structures: Experimental analysis
'American Society of Civil Engineers (ASCE)', 2018Co-Authors: Lodomez Maurine, Dewals Benjamin, Archambeau Pierre, Pirotton Michel, Erpicum SébastienAbstract:peer reviewedUnder relatively low heads, the occurrence of nappe oscillation, also known as nappe vibration, may be observed on Hydraulic Structures with a free overfall, such as weirs, crest gates, and fountains. This phenomenon is characterized by oscillations of the thin flow nappe cascading downstream of the crest and results in a disturbing noise production that increases the environmental and societal impacts of the Hydraulic Structure. Given limited information available regarding the physical processes involved in this phenomenon, a detailed investigation has been undertaken to characterize the flow for free-overfall Structures where nappe oscillation may be of concern. The research is conducted on a prototype-scale linear weir model (weir length of 3.5 m and a fall height of 3 m) using high-speed cameras and audio equipment to characterize the nappe oscillation. The paper presents the quantitative characteristics of the nappe oscillation gained from images and sound analysis, especially in terms of frequency, for aerated and confined nappe configurations. © 2018 American Society of Civil Engineers
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Nappe Vibration Mitigation Techniques for Free-overfall Structrures
2016Co-Authors: Lodomez Maurine, Crookston, Brian M., Pirotton Michel, Tullis, Blake P., Erpicum SébastienAbstract:peer reviewedNappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow Hydraulic Structures operating at low heads, such as fountains, crest gates, and weirs. This phenomenon is visually characterized by oscillations in the thin nappe cascading downstream of the control Structure. These oscillations can produce a significant level of noise and acoustic pressure waves, which can increase the environmental and societal impacts of the Hydraulic Structure. As a result, a detailed investigation has been undertaken to identify practical and effective mitigation solutions for free-overfall Structures where nappe vibration may be of concern. Research is being performed with a prototype-scale linear weir (weir length of 3.5 m and fall height of 3 m) located at the Engineering Hydraulics laboratory of the University of Liège, to assess the effectiveness of various crest modifications and any corresponding impacts to Hydraulic efficiency (i.e., flow rate). The test matrix includes the optimization (position and spacing of elements) of three mitigation solutions which are projecting bolts, deflectors and step. In addition, a high-speed camera and audio equipment have been used to evaluate effectiveness of the configurations in reducing nappe vibration. Finally, this practical study has identified countermeasures suitable for retrofits and new construction, easy to construct, durable, Hydraulically efficient, and with minimal potential for debris collection
