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Scour monitoring for railway assets (UK)
Published in Joan-Ramon Casas, Dan M. Frangopol, Jose Turmo, Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability, 2022
M. Pregnolato, G. Gavriel, D. Thompson, M. Anderson, I. Fox, K. Giles
Scour is an erosional process that can occur in rivers due to natural or man-made events. Natural erosional processes take place in rivers because they act as conduits for the movement of water and sediment. Man-made scour can be caused, by sediment extraction, dam operations, and the influence of any structure placed into the river stream (Pizarro et al., 2020). The flow of water is the leading factor determining whether scour occurs and by how much. Climate change is likely to lead to more frequent and intense flood events which as a result increase the flow of water thus making the scour effect worse (Barkdoll, 2012). In fact, with the evolution of river systems due to climate change, previously unaffected infrastructure could be at risk of scour and currently at-risk structures could become more vulnerable. In addition to direct detection of scour, enhancement of scour prediction by analysis of flood data, catchment models and weather data would be helpful in early detection/prediction of scour.
Structures in maritime locations
Published in A. M. Sowden, The Maintenance of Brick and Stone Masonry Structures, 2020
Increases in ships' draughts can cause problems of bed scour because propellers are very close to dock and channel bottoms. Near to structures this scour can lead to undermining and collapse. Regular bed surveys therefore need to be carried out in order to detect any excessive bed movement before it affects the adjoining structures. Ports which have siltation problems will undertake regular hydrographic sounding surveys to check upon available depths for shipping within docks, at their entrances and in any approach channels. However, such surveys will not necessarily show in sufficient detail all those locations where structures may be at risk because of scour or over-dredging. A check made with a simple lead line or other physical means of direct measurement, in what will inevitably be a fairly small area, is not an expensive exercise. Equally the placing of suitable dense stone on the bed of the waterway can be a comparatively inexpensive way of reducing or eliminating scour.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
General scour is a lowering of the streambed across the waterway at the bridge. This lowering may be uniform across the bed or it may be deeper in some parts of the cross-section. General scour is different from long-term degradation in that general scour may be cyclic and/or related to the passing of a flood. That is, the streambed lowers on the rising limb of a flood and fills on the falling limb. General scour may result from contraction of the flow or from other general scour conditions, such as flow around a bend, variable downstream control, junction of two streams, etc. Contraction scour occurs when the area of the bridge opening is smaller than the flow area of the upstream channel or channel and flood plain. Equations are given in the next section or using sediment transport computer models (see Chapter 97, Sedimentation).
Comparison of risk-based methods for bridge scour management
Published in Sustainable and Resilient Infrastructure, 2023
M. Pregnolato, Pier Francesco Giordano, L.J. Prendergast, P.J. Vardanega, Maria Pina Limongelli
Bridge scour is defined as the erosion of soil from around bridge foundations and abutments, which in turn can lead to a reduction in support capacity (e.g., Ettema et al., 2017; Hager, 2007; Maddison, 2012; Melville & Coleman, 2000; Whitbread et al., 1996; Whitbread et al., 2000); it is a process that may be exacerbated by high river and/or turbulent flows (e.g., due to flooding). The phenomenon of scour includes different types, namely general, contraction/constriction and local scour (Maddison, 2012; Melville & Coleman, 2000). A range of damage mechanisms and failure modes are triggered when scour holes reveal the bottom of or undermine shallow foundations, compromising the integrity and safety of the entire structure (Bento et al., 2018; Bento, Couto, et al., 2022; Mondoro & Frangopol, 2018; Wang et al., 2014). To maintain bridge resilience, owners and operators should consider how best to prevent, detect, and mitigate scour effects (Tubaldi et al., 2022).
Challenges in the application of digital transformation to inspection and maintenance of bridges
Published in Structure and Infrastructure Engineering, 2022
Marcos Massao Futai, Túlio N. Bittencourt, Hermes Carvalho, Duperron M. Ribeiro
Many times, the foundations of bridges currently in service were built before the appearance of modern regulations or based on the prescriptions of expired standards prior to those in force, despite this growing deterioration and the strategic importance of this type of structures, budgets to maintain, repair, and rehabilitate existing foundations are always limited. The phenomenon of scouring is the most common cause of bridge failures related to foundation elements and abutments. In the US, for example, scour accounts for 60% of bridge failures. Scour is the engineering term for erosion and can be defined as the process of soil removal surrounding bridge piers and abutments, especially during floods (Briaud, Gardoni, & Yao, 2014; Medina-Cetina, Yousefpour, & Briaud, 2020). The main consequences of the scouring process are large settlements over time, differential settlements, and loss of bearing capacity of shallow or deep foundations. In more serious situations, abutment scours result in embankment failure.
Evaluation of the predictive performance of general scour equations along the Nile River
Published in ISH Journal of Hydraulic Engineering, 2022
Esam Helal, Hossam El Sersawy, Mahmoud Abdelbaky
In most scour studies, two processes must be considered: natural channel scour, which refers to general scour, and scour induced by man-made structures either in or adjacent to the main river channel, which refers to local scour. The general forms of scour include bend scour, bed form scour, confluence scour, and long-term degradation (Baird et al. 2015). The amount of bed lowering below a supposed natural level (in general, the level of the riverbed before the beginning of the scour) is defined as the scour depth (Alabi 2006). Scouring influences rivers with moveable beds and is often caused by morphological channel changes. Local scouring can result from contraction scour, culvert scour, and scouring around unique structures. Structures can have varying degrees of influence on scouring, which is typically related to a restriction placed on the normal river movement or by turbulence in the typical flow pattern directly related to the structure (Pemberton and Lara 1984).