Sediment Entrainment at High Flow Velocity

Rhee, Cees van

doi:10.1061/(asce)hy.1943-7900.0000214

Cited by 37 publications

(37 citation statements)

References 11 publications

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“…This is in line with the findings of Van Rhee [31]. However, Sidorchuk found the influence of the variability of soil properties like cohesion, aggregate size and soil consolidation to be less important in determining the erosion rate at high flow energy events.…”

Section: Determining Erosion Mechanisms and Rates Of Levee Materialssupporting

confidence: 90%

“…It was noted that under high flow shear stress conditions the infiltration of water into the bed causes for a frictional stress on the particles that contribute to the shear strength of the particles. It was thereby noted that for small particle diameters, the lower hydraulic conductivity caused for a larger stability than in the case of larger particle sizes, making them more resistant to erosion [31] [32]. Higher compacted particles would thereby need to dilate more and hence be more resistant to erosion.…”

Section: Determining Erosion Mechanisms and Rates Of Levee Materialsmentioning

confidence: 99%

“…However, shear stress based approaches like these have often not been validated for high flow velocities. Van Rhee [31] accounts for the effects of dilation by applying a factor to the sediment transport formula of Van Rijn, which is based on a stream power approach. Unlike the shear stress approach, the stream power approach to sediment transport is also valid under supercritical flow conditions.…”

Section: Determining Erosion Mechanisms and Rates Of Levee Materialsmentioning

confidence: 99%

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On the importance of analyzing flood defense failures

et al. 2016

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Abstract. Flood defense failures are rare events but when they do occur lead to significant amounts of damage. The defenses are usually designed for rather low-frequency hydraulic loading and as such typically at least high enough to prevent overflow. When they fail, flood defenses like levees built with modern design codes usually either fail due to wave overtopping or geotechnical failure mechanisms such as instability or internal erosion. Subsequently geotechnical failures could trigger an overflow leading for the breach to grow in size Not only the conditions relevant for these failure mechanisms are highly uncertain, also the model uncertainty in geomechanical, internal erosion models, or breach models are high compared to other structural models. Hence, there is a need for better validation and calibration of models or, in other words, better insight in model uncertainty. As scale effects typically play an important role and full-scale testing is challenging and costly, historic flood defense failures can be used to provide insights into the real failure processes and conditions. The recently initiated SAFElevee project at Delft University of Technology aims to exploit this source of information by performing back analysis of levee failures at different level of detail. Besides detailed process based analyses, the project aims to investigate spatial and temporal patterns in deformation as a function of the hydrodynamic loading using satellite radar interferometry (i.e. PS-InSAR) in order to examine its relation with levee failure mechanisms. The project aims to combine probabilistic approaches with the mechanics of the various relevant failure mechanisms to reduce model uncertainty and propose improvements to assessment and design models. This paper describes the approach of the study to levee breach analysis and the use of satellites for breach initiation analysis, both adopted within the SAFElevee project.

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Section: Determining Erosion Mechanisms and Rates Of Levee Materialssupporting

confidence: 90%

Section: Determining Erosion Mechanisms and Rates Of Levee Materialsmentioning

confidence: 99%

Section: Determining Erosion Mechanisms and Rates Of Levee Materialsmentioning

confidence: 99%

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On the importance of analyzing flood defense failures

et al. 2016

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“…A suction head is trailed over the sea bed and the granular sediment is loosened using water jets. Typical flow velocities are around 30 to 60 m/s (Van Rhee, 2007, 2010. As in the breaching process, the conventional erosion functions also overestimate the erosion rate during jetting.…”

Section: Introductionmentioning

confidence: 99%

Erosion Due to High Flow Velocities: A Description of Relevant Processes

Bisschop

Visser

Rhee

et al. 2011

Int. Conf. Coastal. Eng.

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Convential models for the erosion of non-cohesive sediments overestimate the erosion rate induced by high flow velocities. These high flow velocities occur, for instance, in breaching of embankments or dunes (flow velocities up to 10 m/s) or in jetting sand with a trailing suction hopper dredger (30 to 60 m/s). At these very large flow velocities the erosion process is significantly influenced by the properties of the soil mass (non-cohesive particles). Governing parameters at higher flow velocities are dilatancy, permeability and the (un)drained shear strength of the soil. The sediment concentration in the water also influences the erosion process, especially in case of higher erosion rates. Based on the concept of Van Rhee (2007, 2010) a simple analytical formula is derived that gives a clear insight into the parameters influencing hindered erosion. The concept of hindered erosion is explained by two properties of granular soils: dilatancy and permeability. This implicates that the erosion behaviour of granular soils cannot be described by the behaviour of single particles alone. The properties of the whole soil mass should be considered in predicting erosion at higher flow velocities. Results of a large-scale breach experiment performed in 1994 in the Zwin Channel in the Netherlands (Visser, 1998) are analyzed to evaluate the formula.

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“…Figure 10 shows a cross-section of this dike. The effect of bentonite on the erosion velocity was modelled with the Van Rijn-Van Rhee erosion formula (Equation (10)) (Van Rhee, 2010), by adapting the permeability according to (Visser, 1998) 11…”

Section: Applicationmentioning

confidence: 99%

Retarding the breaching process of dikes

Lemmens¹,

Bisschop²,

Visser³

et al. 2016

Proceedings of the Institution of Civil Engineers - Maritime En

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Dikes constructed from sand generally have a sand core and clay layers on the slopes and the crest to protect the core against erosion. In extreme hydraulic conditions, several failure mechanisms can lead to destruction of the clay layers, exposing the sand core to water. When water overtops the dike and the protective cover of the land-side slope or the crest fails, water flows over the core and erodes the sand. The dike starts to breach, and eventually the land behind the dike is flooded. The rate at which the dimensions of the breach grow influences the rate of inundation of the polder. Reduction of the inundation rate may be achieved by retarding the breaching process. This may reduce the number of casualties, resulting in increasing safety for the inhabitants. In order to achieve, for instance, a safety level ten times higher, mortality has to decrease by a factor of 10. The breaching process can be retarded by reducing the erosion velocity of the sand core. Experiments were executed to investigate the effect on the erosion velocity of adding bentonite to sand. The results of these experiments showed a significant reduction of the permeability and erosion velocity of the sand-bentonite mixtures compared with those of pure sand. The effect of adding bentonite on the breaching process was investigated by applying the Bres model (breach erosion in sand dikes model) to a sand dike tested in a large-scale field experiment (Zwin'94). It was found that adding a small percentage of bentonite reduces the rate of breach growth and the inundation rate in the polder. For the Zwin'94 dike it was determined that 5·4% of bentonite is sufficient to reduce the inundation rate below a threshold value of 0·5 m/h, leading to a significant increase in safety.

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Sediment Entrainment at High Flow Velocity

Cited by 37 publications

References 11 publications

On the importance of analyzing flood defense failures

On the importance of analyzing flood defense failures

Erosion Due to High Flow Velocities: A Description of Relevant Processes

Retarding the breaching process of dikes

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