Depositional Process of Fine Sediments

1982 ◽  
Vol 14 (4-5) ◽  
pp. 175-184 ◽  
Author(s):  
T Kusuda ◽  
T Umita ◽  
K Koga ◽  
H Yorozu ◽  
Y Awaya
Keyword(s):  
Shear Stress ◽  
Particle Diameter ◽  
Critical Diameter ◽  
Sediment Concentration ◽  
Suspended Particles ◽  
Cohesive Sediments ◽  
Fine Sediments ◽  
Annular Flume ◽  
Depositional Process ◽  
Depositional Rate

The main purposes of this study were to investigate the depositional properties of the typical fine less-cohesive sediments in Japanese estuaries and bays and to make it possible to estimate the amount of deposition of the sediments. Suspended fine sediment concentration depends strongly on the shear stress and a critical particle diameter exists corresponding to a certain shear stress. The suspended particles larger than the critical diameter settle down proportionally to the concentration of particles. On the other hand, the suspended particles smaller than the critical diameter are held in water without settling. The depositional properties obtained from experiments make it possible to estimate the depositional rate and amount of the sediments. In the laboratory experiments on deposition, an annular flume with a ring and a channel was used.

Fractal dimensions of cohesive sediment during settling in steady state flow with different initial sediment concentrations

2005 ◽  
Vol 32 (4) ◽  
pp. 658-664 ◽  
Author(s):  
M Stone ◽  
B G Krishnappan
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Suspended Solids ◽  
Fractal Dimensions ◽  
Sediment Concentration ◽  
Cohesive Sediment ◽  
Image Analysis System ◽  
Bed Shear Stress ◽  
Annular Flume ◽  
Over Time

Morphology of particle populations of cohesive sediment were examined during settling experiments in an annular flume with different initial sediment concentrations (200 and 350 mg/L) at constant bed shear stress (0.121 N/m2) using fractal dimensions. The area, longest axis, and perimeter of suspended solids were measured with light microscopy and an image-analysis system to determine three fractal dimensions (D, D1, D2). The ratio between the initial and steady state (time T = 300 min) sediment concentration was 0.54 for both experimental runs and is a function of bed shear stress, not the initial sediment concentration. The fractal dimension D changed from 1.32 at the start of the experiment to 1.36 at steady state, which represents an increase in shape irregularity of larger particles over time compared with smaller particles. At steady state, D1 and D2 were 1.19 and 1.66, respectively. Small increases in D1 and D2 over time indicated a change in morphology towards longer and more elongated particles. The D2 measurements in the present study indicate that differential sedimentation is the predominant flocculation mechanism of cohesive sediments in the flume settling experiments. Fractal dimensions of suspended solids were not significantly different at steady state as a function of initial sediment concentration.Key words: particle morphology, fractal dimensions, cohesive sediment, flocculation, deposition, annular flume.

Modelling Erosion and Deposition of Cohesive Sediments from Hay River, Northwest Territories, Canada

2003 ◽  
Vol 34 (1-2) ◽  
pp. 125-138 ◽  
Author(s):  
David Milburn ◽  
B.G. Krishnappan
Keyword(s):  
Shear Stress ◽  
Northwest Territories ◽  
River Sediment ◽  
Critical Shear Stress ◽  
Cohesive Sediment ◽  
Cohesive Sediments ◽  
Bed Shear Stress ◽  
Flume Experiments ◽  
Annular Flume ◽  
Erosion Processes

A large volume sample of river-bed cohesive sediment and water from Hay River, Northwest Territories, Canada was collected during a spring field program in 2000 as part of a study on under-ice movement of sediment just before breakup. Controlled laboratory experiments were subsequently conducted on the Hay River water/sediments in a rotating annular flume at Burlington, Ontario, Canada to better understand the deposition and erosion processes of cohesive sediment transport. The deposition experiments in the rotating flume confirmed that the Hay River sediment is cohesive and the critical shear stress for deposition and the rates of deposition are a function of bed shear stress and the initial concentration of the sediment in suspension. The erosion experiments provided quantitative data on the critical shear stress for erosion and the rates of erosion as a function of bed shear stress and the age of the sediment deposit. The erosion experiments also indicated that the growth of the biofilm had an influence on the erosion characteristics of the Hay River sediment. Based on the data from the rotating circular flume experiments, a modelling strategy is proposed for calculating the under-ice transport of the cohesive sediments in the Hay River.

scholarly journals The effect of coarse gravel on cohesive sediment entrapment in an annular flume

2015 ◽  
Vol 367 ◽  
pp. 157-162 ◽  
Author(s):  
K. Glasbergen ◽  
M. Stone ◽  
B. Krishnappan ◽  
J. Dixon ◽  
U. Silins
Keyword(s):  
Shear Stress ◽  
Hyporheic Zone ◽  
Critical Shear Stress ◽  
Cohesive Sediment ◽  
Shear Stresses ◽  
Cohesive Sediments ◽  
Gravel Bed ◽  
Gravel Beds ◽  
Annular Flume ◽  
Surface And Pore Water

Abstract. While cohesive sediment generally represents a small fraction (<0.5%) of the total sediment mass stored in gravel-bed rivers, it can strongly influence physical and biogeochemical processes in the hyporheic zone and alter aquatic habitat. This research was conducted to examine mechanisms governing the interaction of cohesive sediments with gravel beds in the Elbow River, Alberta, Canada. A series of erosion and deposition experiments with and without a gravel bed were conducted in a 5-m diameter annular flume. The critical shear stress for deposition and erosion of cohesive sediment without gravel was 0.115 Pa and 0.212 Pa, respectively. In experiments with a gravel bed, cohesive sediment moved from the water column into the gravel bed via the coupling of surface and pore water flow. Once in the gravel bed, cohesive sediments were not mobilized under the maximum applied shear stresses (1.11 Pa) used in the experiment. The gravel bed had an entrapment coefficient (ratio between the entrapment flux and the settling flux) of 0.2. Accordingly, when flow conditions are sufficient to produce a shear stress that will mobilize the armour layer of the gravel bed (>16 Pa), cohesive materials trapped within the gravel bed will be entrained and transported into the Glenmore Reservoir, where sediment-associated nutrients may pose treatment challenges to the drinking water supply.

Effect of Shear Surface Boundaries on Stress for Shearing Flow of Dry Metal Powders—An Experimental Study

1987 ◽  
Vol 109 (2) ◽  
pp. 232-237 ◽  
Author(s):  
K. Craig ◽  
R. H. Buckholz ◽  
G. Domoto
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Normal Stress ◽  
Particle Diameter ◽  
Surface Boundary ◽  
Metal Powders ◽  
Shear Surface ◽  
Shear Cell ◽  
Shearing Flow ◽  
Solids Content

This paper studies the rapid simple shearing flow of dry cohesionless metal powders contained between parallel rotating plates. In this study, an annular shear cell test apparatus was used; the dry metal powders are rapidly sheared by rotating one of the shear surfaces while the other shear surface remains fixed. Such a flow geometry is of interest to tribologists working in the area of dry or powder lubrication. The shear stress and normal stress on the stationary surface are measured as a function of the following parameters: shear surface boundary material and roughness, the shear-cell gap thickness, the shear-rate and the fractional solids content. Both the fractional solids content and the gap thickness are kept at prescribed values during stress measurements. In this experiment the metal powder tested is different from the shear transmission surface material; the effect on the measured normal and shear stress data are reported. The results show the dependence of the normal stress and the shear stress on the shear-rate, particle density and particle diameter. Likewise, a significant stress dependence on both the fractional solids content and the shear-cell gap thickness was observed.

Measuring the onset of mine tailings erosion

2007 ◽  
Vol 44 (4) ◽  
pp. 473-489 ◽  
Author(s):  
M Haneef-Mian ◽  
Ernest K Yanful ◽  
Robert Martinuzzi
Keyword(s):  
Shear Stress ◽  
Power Law ◽  
Mine Tailings ◽  
Laser Doppler Anemometry ◽  
Critical Shear Stress ◽  
Laser Doppler ◽  
Shear Stresses ◽  
Cohesive Sediments ◽  
Fine Grained ◽  
Power Law Equation

The present study gives details of a methodology for estimating the critical shear stress for erosion of mine tailings and other naturally occurring cohesive sediments. Erosion of a cohesive sediments bed occurs when the critical shear stress is exceeded to break the interparticle bond. Experiments were conducted in a 30 cm diameter laboratory column and calibrated using laser Doppler anemometry. The results showed that the erosion pattern of mine tailings particles was similar to those of fine-grained cohesive sediments. A power-law relation of the form E = α[(τ – τcr)/τcr]n is suggested for mine tailings, where E is the erosion rate, α is a coefficient, τ is the shear stress, τcr is the critical shear stress, and n is an exponent. The computed values of α, n, and τcr in the power-law equation were found to be comparable to values derived from experiments in a rotating circular flume. The derived expression for rate of erosion may be incorporated in resuspension and transport models for fine mine tailings of a similar nature.Key words: mine tailings, laser Doppler velocimetry, wall shear stresses, critical shear stress for erosion, erosion – shear stress relationship.

scholarly journals Experimental assessment of Athabasca River cohesive sediment deposition dynamics

2011 ◽  
Vol 46 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Juan Garcia-Aragon ◽  
Ian G. Droppo ◽  
Bommanna Krishnappan ◽  
Brian Trapp ◽  
Christina Jaskot
Keyword(s):  
Oil Sands ◽  
River Sediments ◽  
Quantitative Measure ◽  
River System ◽  
Athabasca River ◽  
Floc Size ◽  
Fine Sediments ◽  
Annular Flume ◽  
Polycyclic Aromatic ◽  
Settling Characteristics

Polycyclic aromatic hydrocarbons (PAHs) originating from natural sources, and potentially from the Athabasca Oil Sands development, are of concern for the Athabasca River and Lake Athabasca delta ecosystems. In order to model the transport of fine sediments (and associated PAHs), it is important to describe the sediment dynamics within the river system. Flocs possess different settling characteristics compared to individual particles. A key aspect in modelling floc settling behaviour is the mathematical linkage of the floc density to floc size. In this paper, a rotating annular flume is used to determine the settling characteristics of Muskeg River (a tributary of the Athabasca River) sediments under different shear conditions. Simulations of the settling and flocculation behaviour of these sediments were used to calibrate a density vs. floc size model. A relationship of the parameters relating floc size and density with the fractal dimension F shows that as diameter increases flocs become weaker. Recommendations for the practical application of the model are further formulated in this paper. The deposition tests offer a quantitative measure of the relative amount of sediment that is likely to be transported through the river for given flow conditions.

Dynamics of Suspended Sediments Related to Fine Particles in Lower Mekong River

2013 ◽  
Vol 446-447 ◽  
pp. 1528-1533
Author(s):  
Sarunya Promkotra
Keyword(s):  
Shear Stress ◽  
Flow Velocity ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Fine Particles ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Mekong River ◽  
Fall Velocity ◽  
Stream Discharge

Analytical results are considered the factors of suspended sediment concentration, fall velocity, dimensionless shear stress, transportation rate and stream discharge. As a result of suspended sediments of Loei, Huang and Mekong River, fine particles account for the applicability in sediment deposits. Floating suspended sediments explicit more clay minerals than suspended sediments. Suspended sediment concentration (SSC) in the estuarine of Loei River and Huang River are moderately less than Mekong River. Flow directions of the interconnected rivers to the mainstream-Mekong River lead to the quantity of SSC. Sediment concentrations attain to the dynamic response. Dimensionless shear stress relates to shear velocity, geometry and grain size of particles, and difference of flow velocity. This shear stress is directly comparative to flow velocity and clay mineral concentrations. The transport rate involves in the flow velocity, SSC and depth of the river. Moreover, stream discharge can be presumed by the geometry of the river and topography of sampling locations.

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