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.

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.

Role of fines on cohesive behavior of mine tailings inferred from critical shear stress

2011 ◽  
Vol 48 (4) ◽  
pp. 568-582 ◽  
Author(s):  
Africa M. Geremew ◽  
Ernest K. Yanful
Keyword(s):  
Shear Stress ◽  
Mine Tailings ◽  
Erosion Rate ◽  
Empirical Relation ◽  
Critical Shear Stress ◽  
Pressure Change ◽  
Laser Doppler Velocimeter ◽  
Shear Stresses ◽  
Boundary Shear ◽  
Boundary Shear Stress

The significance of fines on the cohesive behavior of mine tailings has been investigated by examining the incipient motion of the tailings. Sixteen laboratory experiments were performed in a Plexiglas laboratory annular column on re-constituted mine tailings under a 50 cm water cover. Re-suspension was produced by a Teflon stirrer and the velocity field in the column was characterized using a laser Doppler velocimeter (LDV). The pressure change in the boundary layer was also measured with a Preston tube. It was observed that the nondimensional critical shear stresses showed deviation from those of the noncohesive model results at a fines content greater than 50%–55%. An empirical relation that shows the relation between the boundary shear stress deviation and the percent fines in the tailings was proposed. Regression analysis of the experimental results showed that a power law relationship could reasonably be used to describe the relation between the measured nondimensional excess bed shear stress and the erosion rate. It is proposed that the value of β (the erosion rate constant) could be taken as 1 for mine tailings that show cohesive behavior.

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.

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.

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.

Long-term mineralogical and geochemical evolution of sulfide mine tailings under a shallow water cover

2015 ◽  
Vol 57 ◽  
pp. 178-193 ◽  
Author(s):  
Michael C. Moncur ◽  
Carol J. Ptacek ◽  
Matthew B.J. Lindsay ◽  
David W. Blowes ◽  
John L. Jambor
Keyword(s):  
Shallow Water ◽  
Mine Tailings ◽  
Geochemical Evolution ◽  
Water Cover

ESTIMATION OF CRITICAL SHEAR STRESS OF SEDIMENT USING ROTATIONAL VISCOMETER

2021 ◽  
Vol 77 (2) ◽  
pp. I_1039-I_1044
Author(s):  
Shinya NAKASHITA ◽  
Kyeongmin KIM ◽  
Yuki IMAMURA ◽  
Tadashi HIBINO
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Rotational Viscometer
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