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<p>Scour around bridge piers causes structural instability, posing risks to public safety, economic losses, and environmental damage. The various scour countermeasures developed over the years such as riprap, submerged vanes, sacrificial piles, and collars are few of them. Among these, collars have proven to be effective solutions for local scour reduction. Therefore, this study presents a comprehensive and systematic collar-based countermeasure review of literature from 1992–2025. This study discusses 12 different shapes of collars, highlighting their positions, normalized dimensions, and the percentage of scour reduction from the past literature. It examines the effective elevation (<i>H</i>) of oblong collars (<i>H</i> = −&#xa0;1.0<i>b</i> to 1.0<i>b</i>, where <i>b</i> is pier width) and circular collars (<i>H</i> = −&#xa0;1.0<i>b</i> to 1.3<i>b</i>) as evaluated by various researchers, including their key findings and limitations. Some researchers have developed formulas to calculate temporal (<i>d</i><sub><i>s</i></sub>​) and maximum (<i>d</i><sub><i>sm</i></sub>) scour depths at collar pier structures. In this study, the key parameters such as flow intensity (<i>U</i>/<i>U</i><sub>c</sub>), flow shallowness, collar width (<i>b</i><sub><i>c</i></sub>), and <i>H</i> are analyzed using previous experimental data. The comparative analysis found that oblong collars show less scour below the bed (<i>H</i> = −&#xa0;0.1<i>b</i> and <i>b</i><sub><i>c</i></sub> = 3<i>b</i>, while circular and octagonal collars reduce less <i>d</i><sub><i>sm</i></sub> at bed level (<i>H</i> = 0) when <i>b</i><sub><i>c</i></sub> = 4.5<i>b</i> and 2<i>b</i>. Octagonal collars also show less <i>d</i><sub><i>s</i></sub> reduction compared to others. Researchers suggested that an oblong collar shape reduces scour holes more than rectangular piers. Overall, this review offers effective collar-based scour countermeasures for engineers and researchers.</p>

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A Systematic Review of Collar-based Scour Countermeasures for Bridge Piers

  • 期刊论文

  • 发表日期：

    2025年9月18日

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  • Tania Sultana,
  • Buddhadev Nandi,
  • Subhasish Das

摘要

Scour around bridge piers causes structural instability, posing risks to public safety, economic losses, and environmental damage. The various scour countermeasures developed over the years such as riprap, submerged vanes, sacrificial piles, and collars are few of them. Among these, collars have proven to be effective solutions for local scour reduction. Therefore, this study presents a comprehensive and systematic collar-based countermeasure review of literature from 1992–2025. This study discusses 12 different shapes of collars, highlighting their positions, normalized dimensions, and the percentage of scour reduction from the past literature. It examines the effective elevation (H) of oblong collars (H = − 1.0b to 1.0b, where b is pier width) and circular collars (H = − 1.0b to 1.3b) as evaluated by various researchers, including their key findings and limitations. Some researchers have developed formulas to calculate temporal (ds​) and maximum (dsm) scour depths at collar pier structures. In this study, the key parameters such as flow intensity (U/Uc), flow shallowness, collar width (bc), and H are analyzed using previous experimental data. The comparative analysis found that oblong collars show less scour below the bed (H = − 0.1b and bc = 3b, while circular and octagonal collars reduce less dsm at bed level (H = 0) when bc = 4.5b and 2b. Octagonal collars also show less ds reduction compared to others. Researchers suggested that an oblong collar shape reduces scour holes more than rectangular piers. Overall, this review offers effective collar-based scour countermeasures for engineers and researchers.