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Investigation and assessment of interfaces with earthen levees
Published in Jean-Pierre Tournier, Tony Bennett, Johanne Bibeau, Sustainable and Safe Dams Around the World, 2019
J. Simm, M. Roca Collell, J. Flikweert, R. Tourment, C. Neutz, P. van Steeg
Internal erosion involves the detachment of soil particles and their transport by seepage flow. There are four main internal erosion mechanisms (Morris et al, 2012, ICOLD, 2016, Tournment, 2015): Contact erosion: related to selective erosion of fine particles from the contact with a coarser layer;Backwards erosion: occurring along a decompressed contact area as a result of seepage exiting an unfiltered surface; it leads to retrogressively growing soil piping and sand boils;Concentrated leak erosion: related to the detachment of soil particles through a pre-existing path, such as a crack. This mechanism may be the most important internal erosion process for transitions between soil and hard structures;Suffusion: related to the selective erosion of the fine particles from a matrix of coarse particles.
Dispersion
Published in Alan J. Lutenegger, Laboratory Manual for Geotechnical Characterization of Fine-Grained Soils, 2023
Dispersion tests are a way to determine how easily a soil might become disaggregated. The tests have real consequences, since it may be important to determine if a soil has a tendency to disaggregate easily when it comes into contact with clean water. In natural or compacted soils that may be subjected to water flow, dispersive soils tend to create a condition known as “piping”, which is a form of internal erosion. Piping tends to produce internal flow cavities by washing away soils such as in an earth dam or in backfill around buried pipes. The Double Hydrometer Test is an indicator test giving results that suggest more testing may be needed. The test could also be performed using the pipette method.
A simplified finite element implementation of the Sellmeijer model for backward erosion piping
Published in António S. Cardoso, José L. Borges, Pedro A. Costa, António T. Gomes, José C. Marques, Castorina S. Vieira, Numerical Methods in Geotechnical Engineering IX, 2018
Internal erosion refers to any process by which soil particles are gradually eroded from within or beneath water retaining structures. Accounting for 46 percent of historical dam failures (Foster et al. 2000), internal erosion is an issue of significant concern for geotechnical engineers. Internal erosion can be subdivided into four distinct mechanisms: (1) concentrated leak erosion, (2) backward erosion piping (BEP), (3) contact erosion, and (4) suffusion. BEP accounts for approximately one-third of all internal erosion failures (Richards & Reddy 2007), and is the focus of this study. For further details on the other erosion mechanisms, the interested reader is referred to Bonelli (2013) and ICOLD (2015).
Experimental study on internal erosion and seepage in the foundation of a dike under variable water head
Published in European Journal of Environmental and Civil Engineering, 2022
Pan Ming, Jun Lu, Xin Cai, Miaoyan Liu, Shaowei Hu
Internal erosion mechanisms involve several parameters, such as gradation curve, clay content, confining pressure, pressure paths, and hydraulic conditions. Several authors have carried significant amount of research on the parameters of internal corrosion and obtained many meaningful conclusions. However, still, only very limited information is available on the internal erosion mechanism in hydraulic conditions, especially, under a variable water head. The water level of a river changes yearly. Consequently, the hydraulic conditions of a dike keep changing. At high water levels, when the hydraulic head is above a ‘critical’ value, the seepage flow is sufficient to initiate, transport, and migrate the soil within a dike’s structure (Bridle, 2017). The occurrence of internal erosion changes the microstructure of soils, causes sudden changes in hydraulic and mechanical conditions of the soils (Chang & Zhang, 2013), and induces dam and dike failures. Thus, there is a need for better understanding of the failure mechanism of dikes through internal erosion under varying hydraulic conditions. Therefore, in this research, laboratory erosion experiments under the action of a variable water head were carried out by setting different inflow rates. The hydraulic and mechanical characteristics of the internal erosion process were analysed. In the backward erosion stage, according to the well flow theory and hydraulic balance of the particles, the effect of water head rising rate on the internal erosion was analysed.
New approach to describe hydro-mechanical phenomenon of suffusion: erosion, transport and deposition
Published in European Journal of Environmental and Civil Engineering, 2020
Hashem Abdou, Fabrice Emeriault, Olivier Plé
Suffusion is a process of internal erosion whereby fine grains are removed from a soil due to groundwater flow. This causes a change in the hydraulic and mechanical properties of the soil. This type of internal erosion is triggered in soils which are submitted to a large hydraulic gradient, i.e. levees or earth dams. This type of internal erosion is still an active research topic, e.g. Bonelli and Marot (2008), Bonelli (2011), Monnet, Plé, and Nguyen (2012), Plé, Monnet, and Nguyen (2012), Nguyen, Ple, and Monnet (2013), Papamichos and Vardoulakis (2005), Cyril, Yves-Henri, Remi, and Chia-Chun (2010), Bendahmane, Marot, and Alexis A. (2008), Richards and Reddy (2012), Shwiyhat and Xiao (2010), Xiao and Shwiyhat (2012), Fannin and Moffat (2010), Moffat and Fannin (2006) and Zhang et al (2013). However, most of these authors focussed on characterising the effects of suffusion in laboratory tests. Extension to practical case is done by Reddi (1997) who has reviewed other models developed to describe the particle transport in soils and described their applications.
A method to assess the suffusion susceptibility of low permeability core soils in compacted dams based on construction data
Published in European Journal of Environmental and Civil Engineering, 2019
Lingran Zhang, Rachel Gelet, Didier Marot, Marc Smith, Jean-Marie Konrad
Internal erosion is one of the main causes of embankment dam failures (Foster, Fell, & Spannagle, 2000). Based on the physics of the process and on its location within a structure, four types of internal erosion can be identified: concentrated leak erosion, backward erosion, contact erosion and suffusion (Fry, 2012). Suffusion is a complex process that under seepage flow, the fine solid particles can be detached, transported, and for some of them blocked. The finer fraction eroded and leaving the coarse matrix of the soil will further modify the hydraulic conductivity and mechanical parameters of the soil. On-going suffusion may result in an increase of permeability, greater seepage velocities and potentially higher hydraulic gradients, possibly accelerating the rate of suffusion (Icold, 2013). The development of suffusion gives rise to a wide range of dam incidents including piping and sinkholes.