A design approach for selecting the optimum water cover depth for subaqueous disposal of sulfide mine tailings

2005 ◽  
Vol 42 (1) ◽  
pp. 207-228 ◽  
Author(s):  
Mustafa A Samad ◽  
Ernest K Yanful
Keyword(s):  
Shear Stress ◽  
Mine Tailings ◽  
Wind Waves ◽  
Sediment Resuspension ◽  
Critical Shear Stress ◽  
Linear Wave ◽  
Cover Depth ◽  
Water Cover ◽  
The Impact

The use of shallow water covers to flood reactive mine tailings is one of the most effective and common methods of managing sulfide-rich reactive mine tailings in temperate climates. One of the aspects critical to the success of subaqueous tailings disposal is the water depth required in the pond to maintain desirable water quality. Wind waves and associated pressure-driven currents could resuspend the tailings, which might result in increased oxidation and compromise the quality of the water cover. Although existing methodologies for water cover design are based on eliminating tailings resuspension, sediment-trap data from several sites in Canada still indicate resuspension in most of the ponds. In the present paper, a design methodology is proposed for optimizing the water cover depth, allowing sediment resuspension within regulatory limits. The method uses linear wave theory and countercurrent flow profiles to obtain the total bottom shear stress, which is then compared with the critical shear stress of the tailings to predict the onset of erosion and resuspension and to compute the resulting mass of suspended tailings. Application of the methodology to a tailings pond in British Columbia, Canada, indicates that although a maximum water cover depth of 2.5 m is necessary to eliminate tailings resuspension, a maximum depth of 1.5 m could still be used, as the resulting concentration of suspended tailings remains within the regulatory limit. The methodology also provides an estimate of the impact of resuspension-induced oxidation on the quality of the water cover above the tailings, such as sulfate production.Key words: mine tailings, water cover, wind waves, countercurrent flows, shear stress, resuspension.

Field evidence of resuspension in a mine tailings pond

2001 ◽  
Vol 38 (4) ◽  
pp. 796-808 ◽  
Author(s):  
Celestina Adu-Wusu ◽  
Ernest K Yanful ◽  
Mohammed H Mian
Keyword(s):  
Shear Stress ◽  
Mine Tailings ◽  
Critical Shear Stress ◽  
Field Measurements ◽  
Shear Stresses ◽  
Wind Speeds ◽  
Tailings Pond ◽  
Field Evidence ◽  
Water Cover ◽  
Solubility Of Oxygen

Flooding of tailings under shallow water covers is an effective method of decommissioning potentially acid generating mine tailings. The low diffusivity and solubility of oxygen in water are attractive features of this technology. However, wind-induced waves can resuspend flooded tailings and expose them to greater contact with dissolved oxygen, thereby increasing the potential for oxidation and acid generation. Field measurements of wind activity and waves under different water cover depths and associated resuspension for a mine tailings pond in Ontario are presented and discussed. The results show that wind speeds greater than 8 m/s above water covers that are shallower than 1 m create waves of height greater than 10 cm and bottom shear stresses greater than 0.2 Pa. Under these conditions the critical shear stress of the mine tailings was exceeded, resulting in erosion and subsequent resuspension.Key words: mine tailings, water cover, wind-induced waves, resuspension, wind speed, shear stress.

Behavior of mine tailings under cyclic hydraulic loading

2011 ◽  
Vol 38 (2) ◽  
pp. 131-140 ◽  
Author(s):  
Africa M. Geremew ◽  
Ernest K. Yanful
Keyword(s):  
Shear Stress ◽  
Shallow Water ◽  
Mine Tailings ◽  
Critical Shear Stress ◽  
Pressure Change ◽  
Visual Observation ◽  
Laser Doppler Velocimeter ◽  
Surface Erosion ◽  
Water Cover ◽  
Erosion Equation

Shallow water cover is one of the most effective methods of managing sulfide-bearing reactive mine tailings. Unless sufficient water cover depth is provided, surface erosion by wind-induced waves and pressure-driven currents can re-suspend the tailings and expose them to dissolved oxygen and affect the quality of the water cover. The present study gives a simple approach for the estimation of the critical shear stress for surface erosion of mine tailings and cohesive sediments under shallow water cover. Erosion tests were carried out in a Plexiglas laboratory annular column on mine tailings and sediments under a 50 cm water cover. The annular column was 30 cm in diameter, 120 cm in height and had a 9 cm annular flow width. Shear stress was introduced through a motor driven Teflon stirrer to investigate the initiation of motion and subsequent re-suspension of newly deposited mine tailings and sediments. The velocity field and the pressure change in the boundary layer were measured by laser Doppler velocimeter (LDV) and Preston tube, respectively. The ranges of critical shear stress for the tailings and sediments were estimated by the LDV and Preston tube measurements and visual observation. The results showed that the erosion behavior of most of the mine tailings can be explained by a power law erosion equation.

scholarly journals The impact of particle shape on friction angle and resulting critical shear stress: an example from a coarse-grained, steep, megatidal beach

2013 ◽  
Vol 1 (1) ◽  
pp. 1187-1208 ◽  
Author(s):  
N. Stark ◽  
A. E. Hay ◽  
R. Cheel ◽  
C. B. Lake
Keyword(s):  
Shear Stress ◽  
Particle Motion ◽  
Particle Shape ◽  
Critical Shear Stress ◽  
Friction Angle ◽  
Sediment Dynamics ◽  
Tidal Range ◽  
Strong Increase ◽  
Elliptic Plate ◽  
The Impact

Abstract. The impact of particle shape on the friction angle, and the resulting critical shear stress on sediment dynamics, is still poorly understood. In areas characterized by sediments of specific shape, particularly non-rounded particles, this can lead to large departures from the expected sediment dynamics. The steep slope (1:10) of the mixed sand-gravel beach at Advocate Harbour was found stable in large-scale morphology over decades, despite a high tidal range of ten meters or more, and strong shorebreak action during storms. The Advocate sand (d < 2 mm) was found to have an elliptic, plate-like shape. Exceptionally high friction angles of the material were determined using direct shear, ranging from φ &amp;approx; 41–46°, while the round to angular gravel was characterized by φ = 33°. The addition of 25% of the elliptic sand to the gravel led to an immediate increase of the friction angle to φ = 38°. Furthermore, re-organization of the particles occurred during shearing, being characterized by a short phase of settling and compaction, followed by a pronounced strong dilatory behavior and an accompanying strong increase of shear stress. Long-term shearing (24 h) using a ring shear apparatus led to destruction of the particles without re-compaction. Finally, submerged particle mobilization was simulated using a tilted tray in a tank. Despite a smooth tray surface, particle motion was not initiated until reaching tray tilt angles of 31° and more, being 7° steeper than the latest gravel motion initiation. In conclusion, geotechnical laboratory experiments quantified the important impact of the elliptic, plate-like shape of Advocate Beach sand on the friction angles of both pure sand and sand-gravel mixtures. The resulting effect on initiation of particle motion was confirmed in tilting tray experiments. This makes it a vivid example of how particle shape can contribute to the stabilization of the beachface.

scholarly journals Application of geoinformation techniques to determine zones of sediment resuspension induced by wind waves in lakes (using two lakes from Northern Poland as examples)

2016 ◽  
Vol 16 (1) ◽  
pp. 3-14
Author(s):  
Elżbieta Bajkiewicz-Grabowska ◽  
Maciej Markowski ◽  
Krzysztof Lemańczyk
Keyword(s):  
Lake Water ◽  
Wind Waves ◽  
Sediment Resuspension ◽  
Simulation Method ◽  
Northern Poland ◽  
Gis Tools

Abstract Resuspension in lakes affects the quality of lake water. It is possible to model this process and visualize its outcomes using GIS tools. An assessment of the size of the zone of sediment resuspension was made for two lakes located in Northern Poland threatened by rapid eutrophication. For each of the lakes, four simulations using two methods for determining the effective wind length (F) (Model 1 and Model 2) and two methods for determining the wind wavelength (Lw) (Model A and Model B) were performed. The analysis, taking into account the morphometry of the studied lakes and anemometric conditions, indicated that the differentiator is the applied simulation method of calculating the wavelength caused by the wind. The analysis is theoretical in nature and the results need to be verified in the field..

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.

The influence of bedrock topography on grain entrainment in bedrock-alluvial channels

2020 ◽  
Author(s):  
Rebecca Hodge ◽  
Marcus Buechel ◽  
Sophie Kenmare
Keyword(s):  
Shear Stress ◽  
Surface Topography ◽  
Critical Shear Stress ◽  
Bedload Transport ◽  
Force Balance ◽  
Alluvial Channels ◽  
Bedrock Topography ◽  
Sediment Cover ◽  
Bedrock Surface ◽  
The Impact

&lt;p&gt;Sediment grains in bedrock-alluvial channels can be entrained from bedrock surfaces or from alluvial patches. Field tracer data has shown that grains entrained from different surfaces can have very different critical shear stresses, which will affect bedload transport rates, the stability of sediment cover and bedrock incision. We hypothesise that the topography of the bedrock surface affects the critical shear stress of a sediment grain in at least three ways: the pivot angle through which the grain must move to be mobilised; the extent to which the grain is sheltered by upstream bedrock protrusions; and the impact on the flow profile via the roughness length z&lt;sub&gt;0&lt;/sub&gt;. Here we quantify how bedrock topography affects these three different components, and their overall impact on critical shear stress.&lt;/p&gt;&lt;p&gt;Our analysis is based around six samples of bedrock river topography, from rivers with different degrees of roughness and structural characteristics. Each surface was 3D printed at a reduced scale, and pivot angles were measured by dropping grains of different sizes at different locations, and tilting the surface until the grain moved. For the surface with bedrock ribs, experiments were repeated with the ribs parallel and perpendicular to the downslope direction. Further experiments were performed after incrementally covering 25% through to 100% of the surface with fixed sediment cover. Bedrock sheltering and z&lt;sub&gt;0&lt;/sub&gt; were estimated from analysis of surface topography.&lt;/p&gt;&lt;p&gt;Overall, we find that measured pivot angles decrease with increasing surface roughness, similar to previous relationships from alluvial channels. However, we find that the pivot angle for a grain at any particular location cannot be predicted from the local surface topography, because of the complex interaction between grain shape and the different scales of roughness present on the surface. Rib direction also has a significant influence on mean pivot angle. The impact of sediment cover depends on the relative roughness of the cover and the bedrock surface.&lt;/p&gt;&lt;p&gt;We calculate critical shear stress using Kirchner&amp;#8217;s force balance model, parameterised using our measurements of pivot angle, sheltering and z&lt;sub&gt;0&lt;/sub&gt;. We find that z&lt;sub&gt;0&lt;/sub&gt; has the largest impact on the predicted median values of critical shear stress. Including the measured pivot angles reduces the lowest values of critical shear stress, with implications for the onset of sediment transport. Overall, our data represent the first attempt to quantify fully how bedrock topography influences the critical shear stress of sediment grains in bedrock-alluvial channels.&lt;/p&gt;

Erosion characteristics and stochastic nature of bed shear stress in underwater mine tailings

2017 ◽  
Vol 44 (6) ◽  
pp. 426-440 ◽  
Author(s):  
Africa M. Geremew
Keyword(s):  
Shear Stress ◽  
Mine Tailings ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Critical Shear Stress ◽  
Pressure Change ◽  
Rayleigh Distribution ◽  
Surface Erosion ◽  
Bed Shear Stress ◽  
Stochastic Nature

The erosion of mine tailings was investigated by examining the physical processes during the initiation of motion of the tailings. Erosion experiments were conducted on mine tailings samples and natural soils in a Plexiglas laboratory annular column under 50 cm water cover. Resuspension was introduced with a Teflon stirrer and the bed shear stress was estimated from the measured near-bed velocity field and the pressure change in the boundary layer. Two modes of initiation of motion of cohesive mine tailings that showed cohesive behaviour was noticed: pitting erosion and line erosion and the modes of initiation of motion changed mainly with percentage of fines. At incipient motion of the tailings that showed cohesive behaviour, the pore water pressure distribution showed a relative sudden peak and a decline when the aggregated tailings burst. A four order of magnitude difference was observed between the undrained shear strength and critical shear stress for surface erosion of the tailings. The stochastic nature of the bed shear stress was explained by the Rayleigh distribution that provides an approach for correcting the critical shear stress estimated from the near-bed velocity. This correction is necessary to achieve a conservative estimate of the critical shear stress for design purposes.

scholarly journals A new technology for suspended sediment simulation in Lake Taihu, China: Combination of hydrodynamic modeling and remote sensing

2019 ◽  
Vol 78 (1) ◽  
Author(s):  
Zhuo Zhang ◽  
Changchun Huang ◽  
Fei Guo ◽  
Zhiyao Song ◽  
Di Hu
Keyword(s):  
Remote Sensing ◽  
Shear Stress ◽  
Lake Taihu ◽  
New Technology ◽  
Sediment Resuspension ◽  
Ocean Color ◽  
Critical Shear Stress ◽  
Traditional Model ◽  
Factors Associated ◽  
Remote Sensing Techniques

Sediment resuspension is closely related to the endogenetic release of nutrients in Lake Taihu. Thus, understanding the factors associated with sediment resuspension is important. In this study, a new technology, which integrates a hydrodynamic model and remote sensing techniques, was applied to derive the distribution of the erosion flux and obtain the spatially variable critical shear stress. Then, the spatially variable critical shear stress was used in the sediment simulations at Lake Taihu. Compared to the traditional model, based on uniform values of critical shear stress, the new method, using variable values of critical shear stress calibrated from the Geostationary Ocean Color Imager (GOCI) data, significantly improved the sediment simulations at Lake Taihu. Based on the erosion flux from August 6-8, 2013, the correlations between erosion and wind speed, wind fetch, mud depth, and water depth were analyzed for different subsections and spots in Lake Taihu. The potential sources of error were also addressed. Further improvement of the model is necessary.  

scholarly journals On the Wave Bottom Shear Stress in Shallow Depths: The Role of Wave Period and Bed Roughness

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1348 ◽  
Author(s):  
Sara Pascolo ◽  
Marco Petti ◽  
Silvia Bosa
Keyword(s):  
Shear Stress ◽  
Dynamic Equilibrium ◽  
Dominant Role ◽  
Wind Waves ◽  
Sediment Resuspension ◽  
Growth Curves ◽  
Finite Depth ◽  
Wave Period ◽  
Bed Shear Stress

Lagoons and coastal semi-enclosed basins morphologically evolve depending on local waves, currents, and tidal conditions. In very shallow water depths, typical of tidal flats and mudflats, the bed shear stress due to the wind waves is a key factor governing sediment resuspension. A current line of research focuses on the distribution of wave shear stress with depth, this being a very important aspect related to the dynamic equilibrium of transitional areas. In this work a relevant contribution to this study is provided, by means of the comparison between experimental growth curves which predict the finite depth wave characteristics and the numerical results obtained by means a spectral model. In particular, the dominant role of the bottom friction dissipation is underlined, especially in the presence of irregular and heterogeneous sea beds. The effects of this energy loss on the wave field is investigated, highlighting that both the variability of the wave period and the relative bottom roughness can change the bed shear stress trend substantially.

scholarly journals The Influence of Ship Waves on Sediment Resuspension in the Large Shallow Lake Taihu, China

2020 ◽  
Vol 17 (19) ◽  
pp. 7055
Author(s):  
Minsheng Bu ◽  
Yiping Li ◽  
Jin Wei ◽  
Chunyan Tang
Keyword(s):  
Shear Stress ◽  
Shallow Lakes ◽  
Lake Taihu ◽  
Sediment Resuspension ◽  
Critical Shear Stress ◽  
Wave Disturbance ◽  
Future Research ◽  
Natural State ◽  
Ship Waves ◽  
Ship Wave

Sediment resuspension induces endogenous nutrient release in shallow lakes, which has been demonstrated to be associated with eutrophication. In addition to natural wind-driven resuspension, navigable shallow lakes (such as Lake Taihu, China) also experience resuspension from human activities, such as ship waves. Both processes determine the intensity, frequency, and duration of sediment resuspension, and may consequently affect the pattern of cyanobacteria blooms in the lake. In this study, acoustic Doppler Velocimeter (ADV), Optical Backscatter Sensor (OBS), and temperature wave tide gauge (instrument model :RBR duo TD|wave) were placed in an observation platform in the lake to obtain high-frequency flow velocities, suspended sediment concentration (SSC), and wave parameters before, during, and after a cargo ship passed by. We found that the ship wave disturbance intensity is greatly influenced by the draft depth. The movement generated by ship disturbance is primarily horizontal rather than vertical. Compared with the wind-induced wave, the disturbance caused by the ship waves has a high intensity, short duration, and narrow range of influence. The maximum total shear stress under ship disturbance can reach 9~90 times the critical shear stress under a natural state. Therefore, the effect of ship waves on sediment resuspension near the channel of Lake Taihu is much greater than that of wind-induced waves. These findings represent an important step towards understanding the quantitative relationship between ship wave disturbance and sediment resuspension, and lay the foundation for future research in order to understand and control the eutrophication of shallow lakes.

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