The influence of particle size of the dispersed mineral fraction on the settlement of marine and estuarine muds

Sanchez, Martin; Levacher, Daniel

doi:10.1007/s00367-007-0053-7

Cited by 13 publications

(10 citation statements)

References 21 publications

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“…In comparison with the previous settling tests illustrating other settling regimes, the hindered regime exhibited an initial time during which the front was forming and particles were settling slower than after the front was created (Sanchez and Levacher 2007). This initial time led to flocculation indexes higher than in the case of the free settling regime (IF local between 1 and 4, Fig.…”

Section: Hindered Settling Regimementioning

confidence: 92%

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Using an optical settling column to assess suspension characteristics within the free, flocculation, and hindered settling regimes

et al. 2015

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Purpose Instruments able to measure the settling velocity distribution (SVD) and investigate the flocculation behavior of suspensions for a wide range of concentrations and settling regimes are required to understand and model sediment transport in headwater catchments. Such knowledge will improve our water resource management capabilities. Materials and methods An optical settling column, equipped with a vertical array of optical sensors, was used to provide light transmission through a suspension during quiescent settling. A new method to determine the settling velocity and the propensity of suspensions to flocculate is proposed. Its reliability was evaluated based on settling tests for (1) noncohesive sediments, (2) cohesive sediments at medium (~1 g l −1 ) concentration in a natural and deflocculated state, and (3) a cohesive sediment at a very high concentration (~10 g l −1 ). This choice of sediments and concentrations allowed for the assessment of free, flocculated, and hindered settling regimes. Results and discussion The proposed data processing method provides measurements for a range of test conditions. The result showed that different populations of particles with different settling behaviors can be identified within the suspensions. In the case of noncohesive sediments, the proposed method provided SVD similar to those obtained with reference methods. The propensity to flocculate was zero as expected for inert material. The natural cohesive sediment at medium concentration exhibited a large range of SVD (10 −2 -10 −5 m s −1 ) and high propensity to flocculate. These were both reduced with the addition of a deflocculant. Identified particle behaviors were consistent with independent measurement of size distribution, microscopic, and erosion properties. In the hindered regime, a narrow SVD corresponded to the hindered front settling velocity (~10 −4 m s −1 ). Conclusions An optical settling column was able to provide reliable SVD and an evaluation of the propensity of particles to flocculate. The settling column was able to detect variations of the settling velocities with settled depth, thus highlighting that settling columns with a single measurement point may provide erroneous results by not accounting for the full spectrum of settling depth.

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Section: Hindered Settling Regimementioning

confidence: 92%

“…All particles settle at the same bulk velocity (Sanchez and Levacher 2007) depending on the cohesion and concentration of the suspension (Camenen and Pham Van Bang 2011; Van and Pham Van Bang 2013). During settling in quiescent condition, a clear interface (front), associated with a strong drop of SSC, is formed.…”

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confidence: 99%

Using an optical settling column to assess suspension characteristics within the free, flocculation, and hindered settling regimes

et al. 2015

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“…Yet some existing parameterizations take into account the density and volume of primary particles (Atkinson et al ., ); however, these parameters are usually not the core of such models. Nonetheless, it has been experimentally suggested that settling velocity of estuarine muds is influenced by elementary particles characteristics that, in turn, are highly dependent upon the nature of the source material (Sanchez and Levacher, ).…”

Section: Introductionmentioning

confidence: 99%

From soil aggregates to riverine flocs: a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics

Grangeon

Droppo

Legoût

et al. 2013

Hydrological Processes

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Abstract:Particles eroded from hillslopes and exported to rivers are recognized to be composite particles of high internal complexity. Their architecture and composition are known to influence their transport behaviour within the water column relative to discrete particles. To-date, hillslope erosion studies consider aggregates to be stable once they are detached from the soil matrix. However, lowland rivers and estuaries studies often suggest that particle structure and dynamics are controlled by flocculation within the water column. In order to improve the understanding of particle dynamics along the continuum from hillslopes to the lowland river environment, soil particle behaviour was tested under controlled laboratory conditions. Seven flume erosion and deposition experiments, designed to simulate a natural erosive event, and five shear cell experiments were performed using three contrasting materials: two of them were poorly developed and as such can not be considered as soils, whilst the third one was a calcareous brown soil. These experiments revealed that soil aggregates were prone to disaggregation within the water column and that flocculation may affect their size distribution during transport. Large differences in effective particle size were found between soil types during the rising limb of the bed shear stress sequence. Indeed, at the maximum applied bed shear stress, the aggregated particles median diameter was found to be three times larger for the well-developed soil than for the two others. Differences were smaller in the falling limb, suggesting that soil aggregates underwent structural changes. However, characterization of particles strength parameters showed that these changes did not fully turn soil aggregates into flocs, but rather into hybrid soil aggregate-floc particles.

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“…Les coefficients de perméabilité sont de plus en plus faibles alors que les concentrations sont élevées. Ces dernières sont du même ordre que les perméabilités des sédiments marins méditerranéens (SANCHEZ & LEVACHER, 2007 ;LEVACHER et al, 2011).…”

Section: La Décantationunclassified

Caractérisation physique et environnementale des sédiments du port de pêche de Sfax

Feki¹,

Mbarka²

2015

Edition 3, Ferrare, Italie

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Résumé :Le dragage des sédiments dans les ports est indispensable pour assurer le bon fonctionnement du trafic. Le port de pêche de Sfax en Tunisie est parmi les grands ports à l'échelle de l'Afrique. Les quantités draguées tous les 10 ans sont importantes et sont clapés en mer sans traitement préalable. Pour une éventuelle valorisation de ces sédiments dans des applications civiles, il est nécessaire de disposer des caractéristiques physique et mécanique de ces sédiments. Pour éviter tout risque de pollution il est aussi nécessaire d'évaluer leur degré de contamination en éléments polluants. Dans cet objectif, des échantillons sont prélevés dans le port de pêche de Sfax. Une première partie est consacrée à la caractérisation physico-chimique des sédiments. La deuxième partie s'intéresse à suivre le phénomène de décantation et d'étudier la variation de la perméabilité des sédiments en fonction de leurs concentrations.

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The influence of particle size of the dispersed mineral fraction on the settlement of marine and estuarine muds

Cited by 13 publications

References 21 publications

Using an optical settling column to assess suspension characteristics within the free, flocculation, and hindered settling regimes

Using an optical settling column to assess suspension characteristics within the free, flocculation, and hindered settling regimes

From soil aggregates to riverine flocs: a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics

Caractérisation physique et environnementale des sédiments du port de pêche de Sfax

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