Bridge scour

Résumé

Bridge scour is the removal of sediment such as sand and gravel from around bridge abutments or piers. Hydrodynamic scour, caused by fast flowing water, can carve out scour holes, compromising the integrity of a structure. In the United States, bridge scour is one of the three main causes of bridge failure (the others being collision and overloading). It has been estimated that 60% of all bridge failures result from scour and other hydraulic-related causes. It is the most common cause of highway bridge failure in the United States, where 46 of 86 major bridge failures resulted from scour near piers from 1961 to 1976. Areas affected by scour Water normally flows faster around piers and abutments making them susceptible to local scour. At bridge openings, contraction scour can occur when water accelerates as it flows through an opening that is narrower than the channel upstream from the bridge. Degradation scour occurs both upstream and downstream from a bridge over large a

Source officielle

https://en.wikipedia.org/wiki/Bridge_scour

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Publications associées (38)

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Séances de cours associées (8)

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Experimental study of local scour by a plane jet issuing from a sluice gate

Adhy Kurniawan

EPFL2004

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Velocity and turbulence measurements in a scour hole using an Acoustic Doppler Velocity Profiler

Adhy Kurniawan

2002

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Curved reaches and bends are a characteristic feature of rivers and channels. Their morphology is heterogeneous and typically includes a point bar at the inner side of bends, and bend scour at the outer side. Curvature-induced secondary flow, also called spiral flow or helical flow, is known to play an important role in the generation of this morphological heterogeneity. This secondary flow is outward directed in the upper part of the water column, and causes an increase of velocities and erosive capacity at the outer side of the channel. Near the outer bank, the secondary flow has an important vertical component that impinges on the channel bed and enhances bend scour. The eroded sediment is then transported in inward direction by the near-bed component of the secondary flow, and contributes to the development of the point bar at the inner side of the channel. The morphological heterogeneity has adverse effects: scour at the outer side of the bend threatens the stability of the bank and structures like bridge abutments or piers, and deposition of sediment at the inner side of the bend reduces the navigable width. Therefore, river engineers have always tried to attenuate this morphological heterogeneity, for example by artificially roughening the outer bank in order to reduce near-bank velocities, or deflecting the flow away from the outer bank by means of groynes or bottom vanes. All these techniques involved permanent fixed structures. Dr. Violaine Dugué has investigated an innovative technique that is reversible and does not involve fixed structures. It consists in generating an air-bubble screen with a porous tube that is positioned parallel to the outer bank. The rising air-bubbles generate a secondary flow that is opposed to the curvature-induced secondary flow, and thereby reduces the morphological heterogeneity. Dr. Violaine Dugué has performed a series of laboratory experiments with increasing degree of complexity, including straight and curved flows under various conditions of sediment transport. These experiments provided insight in the mutual interactions between the main flow, the curvature-induced flow components, the bubble-screen induced flow components, the sediment transport and the morphology. Based on this novel insight, Dr. Violaine Dugué has developed a methodology that allows quantifying the application range of the bubble-screen technique. It relates the required air discharge of the bubble screen to the geometric and hydraulic characteristics of the open-channel bend. The methodology is illustrated by means of two case studies.

EPFL - LCH2013

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EPFL - LCH2013