Long contraction scour

The most common cause of bridge structure damage in the world today is due to a natural phenomenon called “scouring”. Contraction scour is usually the main concern when it comes to constructing hydraulic structure such as bridges, barrages, cross drainage and weirs. Scour holes are formed at the str...

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Main Author: Koh, Chun Wei
Other Authors: Lim Siow Yong
Format: Final Year Project
Language:English
Published: Nanyang Technological University 2020
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Online Access:https://hdl.handle.net/10356/136736
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1367362020-01-14T07:27:49Z Long contraction scour Koh, Chun Wei Lim Siow Yong School of Civil and Environmental Engineering CSYLIM@ntu.edu.sg Engineering::Civil engineering::Water resources The most common cause of bridge structure damage in the world today is due to a natural phenomenon called “scouring”. Contraction scour is usually the main concern when it comes to constructing hydraulic structure such as bridges, barrages, cross drainage and weirs. Scour holes are formed at the structure abutment due to the erosive action of flowing water through the river channel that has resulted in the removal of sediments on erodible beds. These scour holes will affect the structure stability and its lateral bearing capacity, which eventually leads to the collapse of the bridge. Therefore, it is important to understand this phenomenon in order to maintain the durability and life of hydraulic structure. Hence, the objective of this study is to study the phenomenon of long and gradual contraction scouring in an open channel flow. Results obtained from experiments by past researchers were utilised to carry out a dimensional analysis on the relevant variables that affect the size and depth of scouring. Using the incomplete self-similarity method and regression analysis of the database, a predictive scour depth equation was proposed which is suitable for applications with uniform and non-uniform sediments. It was found that the maximum scour depth in a long contraction depends mainly on the effect of the densimetric Froude number (Fo,d84), width ratio of the uncontracted to the contracted channel (B1/B2), sediment gradation (σg), and the relative sediment size (d84/h1). From the proposed equation 4.5, it able to correlate all the 206 data of uniform and non-uniform sediments and fall within ± 30% range with R2 value of 0.8. Bachelor of Engineering (Civil) 2020-01-14T07:27:49Z 2020-01-14T07:27:49Z 2019 Final Year Project (FYP) https://hdl.handle.net/10356/136736 en application/pdf Nanyang Technological University
institution Nanyang Technological University
building NTU Library
country Singapore
collection DR-NTU
language English
topic Engineering::Civil engineering::Water resources
spellingShingle Engineering::Civil engineering::Water resources
Koh, Chun Wei
Long contraction scour
description The most common cause of bridge structure damage in the world today is due to a natural phenomenon called “scouring”. Contraction scour is usually the main concern when it comes to constructing hydraulic structure such as bridges, barrages, cross drainage and weirs. Scour holes are formed at the structure abutment due to the erosive action of flowing water through the river channel that has resulted in the removal of sediments on erodible beds. These scour holes will affect the structure stability and its lateral bearing capacity, which eventually leads to the collapse of the bridge. Therefore, it is important to understand this phenomenon in order to maintain the durability and life of hydraulic structure. Hence, the objective of this study is to study the phenomenon of long and gradual contraction scouring in an open channel flow. Results obtained from experiments by past researchers were utilised to carry out a dimensional analysis on the relevant variables that affect the size and depth of scouring. Using the incomplete self-similarity method and regression analysis of the database, a predictive scour depth equation was proposed which is suitable for applications with uniform and non-uniform sediments. It was found that the maximum scour depth in a long contraction depends mainly on the effect of the densimetric Froude number (Fo,d84), width ratio of the uncontracted to the contracted channel (B1/B2), sediment gradation (σg), and the relative sediment size (d84/h1). From the proposed equation 4.5, it able to correlate all the 206 data of uniform and non-uniform sediments and fall within ± 30% range with R2 value of 0.8.
author2 Lim Siow Yong
author_facet Lim Siow Yong
Koh, Chun Wei
format Final Year Project
author Koh, Chun Wei
author_sort Koh, Chun Wei
title Long contraction scour
title_short Long contraction scour
title_full Long contraction scour
title_fullStr Long contraction scour
title_full_unstemmed Long contraction scour
title_sort long contraction scour
publisher Nanyang Technological University
publishDate 2020
url https://hdl.handle.net/10356/136736
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