Field Rheology of Mine Tailings & Practical Applications Tailings & Mine Waste 12 Keystone, Colorado Lawrence Charlebois
Overview Field Rheology Significance Field Methods & Natural Analogues Flow Mapping Applications `pahoehoe to paste`
Terminology For this Presentation: Tailings = Heavy Slurries and Thickened Tailings Beaches = Above-Water (Sub-aerial) Tailings Deposits Formed by Flowing Tailings Rheology =.
Rheology Definition 1: the study of the flow of matter Definition 2: the flow behaviour of mine tailings on abovewater beaches Not in this Presentation: In-Pipe Computational Fluid Dynamics Pump / Pipeline Design
y/v y/v Significance of Field Rheology How Far Will the Tailings Flow? How to Manage Different Flavours of Tailings on the Beach? What Will the Beaches Look Like? Which Beach Development Models are Applicable? What-If Scenarios (e.g. Impoundment Failure) Normalized Flocculated MFT Profiles 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 S1C6 = Cell 6S S5A = Cell D1 S4A S4B S4C S5B S2C9 (1) S2C9 (2) c = 1.5 c = 2 c = 2.5 1:1 Reference 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x/h 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 (a) c = 2.5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x/h
Field vs. Laboratory Often Similar Results Neither Fully Satisfy Design/Operational Needs Laboratory Better Suited for Test Matrices on Small Volumes (Design) Field Better Suited for Understanding Operational Variability (Design & Operation) Field Tests are Simple & Inexpensive
Opportunities for Field Rheology Pilot-Scale Testing Large Flumes Test Paddocks During Operation Testing at the Point of Discharge Testing Along Beach Length (e.g. with scaffolding access)
Field Methods Bucket Rheometer Slump Standard Modified Dynamic Slump & Flow Observational Methods
Bucket Rheometer Bucket Measure of: Yield Stress & Apparent Viscosity Large Sample Volume Required Shear Rate Controlled Vane See Fisher et al. 2007 Tailings
Standard Slump Test (Abrams Cone) Measure of: Yield Stress Uses Basic Principles Relatively Large Sample Volume Required ASTM C143
Modified ( Boger ) Slump Test Measure of: Yield Stress Uses Basic Principles Small Sample Volume Required See Pashias & Boger 1996
Dynamic Slump Test Measure of: Yield Stress & Viscosity Uses Basic Principles 4-Dimensional (Slump over Time) Small Sample Volume Required Based on ASTM C1611 t 0 t 1 t 2
Observational / Empirical Methods Natural Analogues for Mine Tailings Flows Lava flows Mudflows Methods from Earth Sciences (Sedimentology, Volcanology, etc.) Empirical Channel and Levee Geometry Relationships Flow Velocity vs. Depth vs. Run-out Relationships
Studying Lava Flows Human Fascination Abundant Research Natural Hazard Abundant Research Complex, Multi-Phase, Highly Viscous Flows (Gas, Liquid, Solids) Use Remote Methods or Study in Retrospect Flow Models Based on Rheology & Energy See Hulme, Griffiths, etc.
Lessons from Lava Flows v = μ = ρgt 2 3μ sin (α) ρgt 2 3v sin (i) Nichols 1939, Griffiths 2000 (after Jeffreys 1925) d = τ y ρg tan (i) Hulme 1974 w = τ y 2ρg tan (i) 2 Griffiths 2000
Elevation relative to Channel Bottom (cm) Lessons from Lava Flows Lava Flowing in Channels Creates Levees (Elevated Banks) Parallel to Flow Process Similar to Flood Plain Aggradation (Overbanking) Geometry of Levees Related to Rheology 30 25 20 15 channel a channel b channel c channel d sem-circle Overbanking & Aggradation 10 dmft 5 0-30 -20-10 0 10 20 30 Offset from Channel Centreline (cm) Channel Sedimentation
Studying Mudflows Similar Constituents to Mine Tailings Natural Hazard Abundant Research Often Studied in Retrospect, Rarely During the Flow Flow Models Based on Rheology & Energy See Coussot 1997, 2005
Solids Volume Fraction Lessons from Mudflows Colloidal Effects Inertial Effects Brownian Effects Hydrodynamic Effects Shear Rate Conceptual model of momentum transfer effects in a suspension (after Coussot, 1997)
Practical Applications of Field Rheology Managing Flow Behaviour (e.g. sustaining sheet-like flow) Adapting Tailings to Different Deposition Environments (e.g. short vs. long beaches) Forecasting & Managing Beach Profiles Optimizing Storage Creating Safe, Stable Deposits
Flow Mapping of Mine Tailings Flow Behaviour Determined by Rheology & Energy Different Flow Regimes Possible Some Desirable, Others Not Can Manipulate Either Rheology or Flow Energy for Desired Results
A Hypothetical Flow Map FLOW TYPE 1 Rheology FLOW TYPE 2 FLOW TYPE 3 FLOW TYPE 4 Flow Energy
A Hypothetical Flow Map FLOW TYPE 1 Dynamic or Static Yield Stress FLOW TYPE 2 FLOW TYPE 3 FLOW TYPE 4 Flow Energy
A Hypothetical Flow Map FLOW TYPE 1 Dynamic or Static Yield Stress FLOW TYPE 2 FLOW TYPE 3 FLOW TYPE 4 Stream Velocity
A Hypothetical Flow Map FLOW TYPE 1 Dynamic or Static Yield Stress FLOW TYPE 2 FLOW TYPE 3 FLOW TYPE 4 Discharge Rate
Boundaries & Transitions FLOW TYPE 1 Yield Stress FLOW TYPE 2 FLOW TYPE 3 FLOW TYPE 4 Stream Kinetic Energy
Flow Maps & Beach Formation Models FLOW TYPE 1 Lubrication Theory (Simms, 2009) Rheology FLOW TYPE 2 Uniform Channel Flow (McPhail 1994; Fitton 2007) FLOW TYPE 3 FLOW TYPE 4 Beach Erosion? Flow Energy
Flow Maps & Failure FLOW TYPE 1 Relatively Slow, Localized, Creeping Failure Rheology FLOW TYPE 2 Destructive Flow, Far Reaching FLOW TYPE 3 FLOW TYPE 4 Catastrophic Flow? Flow Energy
Closing Remarks Field Rheology Provides Meaningful Results Compliments Laboratory Testing Flow Mapping Is a Tool for: Flow Control Beach Management Flow/Beach Development Modelling Failure Risk Assessment Miners Can & Should Learn from Other Earth Sciences
QUESTIONS & DISCUSSION Thank You. 29