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.

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.

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.

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.

Development of a Three-Dimensional Iterative Methodology Using a Commercial CFD Code for Flow Scouring Around Bridge Piers

2012 ◽  
Author(s):  
Phani Ganesh Elapolu ◽  
Pradip Majumdar ◽  
Steven A. Lottes ◽  
Milivoje Kostic
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Critical Shear Stress ◽  
Shear Stresses ◽  
Computational Domain ◽  
Time Step ◽  
Mesh Morphing ◽  
River Bed ◽  
Scour Hole ◽  
The Stability

One of the major concerns affecting the safety of bridges with foundation supports in river-beds is the scouring of river-bed material from bridge supports during floods. Scour is the engineering term for the erosion caused by water around bridge elements such as piers, monopiles, or abutments. Scour holes around a monopile can jeopardize the stability of the whole structure and will require deeper piling or local armoring of the river-bed. About 500,000 bridges in the National Bridge Registry are over waterways. Many of these are considered as vulnerable to scour, about five percent are classified as scour critical, and over the last 30 years bridge failures caused by foundation scour have averaged about one every two weeks. Therefore it is of great importance to predict the correct scour development for a given bridge and flood conditions. Apart from saving time and money, integrity of bridges are important in ensuring public safety. Recent advances in computing boundary motion in combination with mesh morphing to maintain mesh quality in computational fluid dynamic analysis can be applied to predict the scour hole development, analyze the local scour phenomenon, and predict the scour hole shape and size around a pier. The main objective of the present study was to develop and implement a three dimensional iterative procedure to predict the scour hole formation around a cylindrical pier using the mesh morphing capabilities in the STARCCM+ commercial CFD code. A computational methodology has been developed using Python and Java Macros and implemented using a Bash script on a LINUX high performance computer cluster. An implicit unsteady approach was used to obtain the bed shear stresses. The mesh was iteratively deformed towards the equilibrium scour position based on the excess shear stress above the critical shear stress (supercritical shear stress). The model solves the flow field using Reynolds Averaged Navier-Stokes (RANS) equations, and the standard k–ε turbulence model. The iterative process involves stretching (morphing) a meshed domain after every time step, away from the bottom where scouring flow parameters are supercritical, and remeshing the relevant computational domain after a certain number of time steps when the morphed mesh compromises the stability of further simulation. The simulation model was validated by comparing results with limited experimental data available in the literature.

The LABEREX chamber for studying the critical shear stress for fine-grained sediment

1999 ◽  
Vol 99 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Lars Chresten Lund-Hansen ◽  
Christian Christiansen ◽  
Ole Jensen ◽  
Mario Laima
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Fine Grained

Critical Shear Stress for Deposition of Cohesive Sediments in Mai Po

2006 ◽  
Vol 18 (3) ◽  
pp. 300-305 ◽  
Author(s):  
WY CHAN ◽  
Onyx WH WAI ◽  
YS LI
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Cohesive Sediments

Initiation of motion conditions for shale sediments

1983 ◽  
Vol 10 (3) ◽  
pp. 549-554 ◽  
Author(s):  
L. Magalhaes ◽  
T. S. Chau
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Shear Stresses ◽  
Single Particles ◽  
Channel Stability ◽  
High Lift ◽  
Flume Tests ◽  
Load Transport ◽  
Bed Load Transport ◽  
Bed Material

Critical shear stresses for erosion of alluvial shale particles were investigated in a laboratory flume. Tests in the incipient motion conditions of individual particles showed that entrainment of shale bed particles takes place at mean shear stress values 40–50% smaller than other types of non-cohesive and coarse granular material. The low density and platy shape of the shale particles may induce high lift forces, which would account for a decrease in the resistance to erosion of shale channels and greater rates of bed-load transport. Keywords: channel stability, critical shear stress, flume tests, initiation of motion, shale gravels, single particles, weak bed material movement.

Critical Shear Stress for Deposition of Cohesive Sediments in Mai Po

2006 ◽  
Vol 18 (S1) ◽  
pp. 294-299
Author(s):  
W. Y. Chan ◽  
Onyx W. H. Wai ◽  
Y. S. Li
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Cohesive Sediments

Critical Shear Stresses of Sunken Oils

2014 ◽  
Vol 2014 (1) ◽  
pp. 300241
Author(s):  
Charles Watkins ◽  
Olivia Jobin ◽  
Nancy Kinner ◽  
Thomas Ballestero ◽  
Neil W. Thomas ◽  
...  
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Critical Shear Stress ◽  
Water Current ◽  
Shear Stresses ◽  
High Definition ◽  
Annular Flume ◽  
The University ◽  
University Of New Hampshire ◽  
Sunken Oil

As observed in several recent cases (e.g., DBL-152, Enbridge-Kalamazoo), under certain circumstances, spilled oil can sink to the bottom of a water body. Once on the bottom, the oil can move or even remobilize into the water column. The critical shear stress (CSS) is used to accurately predict the movement of sunken oil along and off the bottom. Unfortunately, shear stress has only been measured for one sunken oil (Hibernian Crude API = 34). The Coastal Response Research Center (CRRC) at the University of New Hampshire (UNH) has an annular flume equipped with high-definition cameras and an acoustic velocimeter that can be used to estimate CSS by measuring the instantaneous, three-dimensional water current velocities at which sunken oils move and erode as visible oil droplets. The results reported are for an Alberta bitumen, tested at temperatures between 5° and 28°C in freshwater.

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