Tailings Storage Facilities (TSFs) are among the most critical and closely scrutinized components of modern mining operations. Their design, operation, and closure require a multidisciplinary understanding of geotechnical engineering, hydrology, environmental science, and risk management.
As the industry continues to place greater emphasis on safety, sustainability, and regulatory compliance, a clear understanding of TSF-related terminology has become essential for engineers, students, and professionals involved in mining and tailings management.
This write-up presents a structured glossary of key terminologies used in tailings engineering. It is intended to provide clarity, improve communication, and support technical learning across the various aspects of TSF design, monitoring, performance evaluation, and closure.
Core Terms
Tailings Storage Facility (TSF): The engineered system used to store tailings.
Impoundment: The storage area where tailings are deposited.
Embankment / Dam: The retaining structure.
Starter Dam: Initial embankment used to begin deposition.
Crest: Top of the dam.
Toe: Bottom outer edge of the embankment.
Freeboard: Vertical distance between pond level and crest.
Supernatant Pond: Water pond on top of deposited tailings.
Beach: Sloped surface of deposited tailings.
Spigotting: Discharge of tailings slurry from pipelines.
Decant System: Water recovery structure (tower, barge, or pipe system).
Permeability: A measure of how easily water can flow through soil or tailings.
Brittle Failure: A sudden failure that occurs with little prior deformation or warning.
Geotechnical Design
Shear Strength: The resistance of soil or tailings to sliding along a failure surface, controlled by cohesion and friction between particles.
Undrained Shear Strength: The shear strength of saturated soil when loading occurs so quickly that water cannot drain from the pores.
Consolidation: Excess pore water pressure dissipates from tailings over time.
Pore Water Pressure: The pressure exerted by water within the void spaces of tailings, which influences effective stress and strength.
Phreatic Surface: The boundary within soil tailings that separates saturated material below from unsaturated material above.
Liquefaction Potential: Saturated loose tailings losing strength and behaving like a fluid under loading or disturbance.
Factor of Safety: The ratio of resisting forces to driving forces acting on a slope.
Static vs. Seismic Stability: Evaluating slope stability under normal conditions, while seismic stability assesses behaviour during earthquake loading.
Slope Stability Analysis: Used to determine whether a slope or dam is likely to fail.
Seepage Analysis: Study of water flow through tailings to evaluate pore pressure distribution.
Critical State: A condition where soil continues to deform under constant stress without changing volume.
Hydraulic & Operational Design
Water Balance: Accounting of all water entering, stored in, and leaving a tailings facility.
Storm Event: A rainfall or flood event defined by its probability or maximum possible magnitude for design purposes.
Inflow Design Flood (IDF): The flood magnitude that a dam must safely contain without failure.
Runoff Coefficient: The proportion of rainfall that becomes surface runoff instead of infiltrating the ground.
Return Water: Water recovered from the tailings facility and reused in the mineral processing plant.
Underdrain System: A drainage system beneath a tailings dam that collects and controls seepage.
Filter and Drain Zones: Engineered layers in a dam that prevent soil movement while allowing water to drain.
Upstream Method: A tailings dam construction method where each new embankment raise is built on previously deposited tailings toward the upstream direction.
Downstream Method: A construction method where each embankment raise is built outward on the downstream side using compacted fill material.
Centerline Method: A construction method in which embankment raises are built vertically above the dam crest, maintaining the dam’s centerline.
Deposition & Tailing Types
Deposition Strategy: A method of placing tailings to control stability, drainage, and beach formation.
Cyclic Deposition: Alternating discharge locations over time to improve drying and consolidation of tailings.
Thin Lift Deposition: Placing tailings in thin layers to enhance drainage and accelerate strength gain.
Perimeter Discharge: Discharging tailings along the facility perimeter to form beaches and move water toward the center.
Central Discharge: Depositing tailings from the center of the facility with water collecting near the edges.
Stacking Rate: The rate at which tailings accumulate within the storage facility.
Beach Angle: The slope formed by deposited tailings between the discharge point and the pond.
Conventional Slurry: Tailings are transported and deposited as a low-density slurry with high water content.
Thickened Tailings: Tailings with higher solids concentration are produced by removing excess water.
Paste Tailings: Highly thickened tailings with yield stress that behave like a paste during transport.
Filtered Tailings: Tailings with most water removed by filtration before disposal.
Embankment & Dam Components
Core Zone: A low-permeability section of the dam designed to control seepage through the structure.
Shell Zone: The outer structural zone of the dam that provides stability and support.
Filter Zone: A granular layer that prevents fine particles from migrating while allowing water to pass.
Drain Zone: A highly permeable layer designed to safely drain seepage water.
Toe Drain: A drainage system located at the downstream toe of the dam to collect seepage.
Seepage Collection System: Infrastructure used to collect and manage water exiting the dam.
Drainage Blanket: A horizontal drainage layer placed beneath tailings or embankments to control seepage.
Cut-Off Trench: An excavated trench filled with low-permeability material to reduce seepage beneath the dam.
Grout Curtain: A subsurface barrier created by pressure-injecting grout into rock or soil to reduce seepage.
Trigger Action Response Plan (TARP): A predefined plan outlining actions when monitoring thresholds are exceeded.
Post-Closure Monitoring: Long-term monitoring of tailings facilities after mine closure.
Long-Term Water Management: Control of water flow and storage after mining operations end.
Monitoring & Instrumentation
Piezometer: An instrument used to measure pore water pressure within soil, tailings, or dam structures.
Inclinometer: A device used to measure ground or slope movement within embankments.
Settlement Plate: A device used to monitor the vertical settlement of tailings or foundation soils.
Survey Prism: A reflective target used in surveying to track structural movement.
Remote Sensing: The collection of data using sensors mounted on satellites, drones, or aircraft without direct contact.
Satellite Deformation Monitoring: The use of satellite imagery to detect and measure movement over time.
InSAR Monitoring: A satellite-based technique used to detect very small ground deformations by comparing radar images over time.
Real-Time Monitoring: A system that continuously collects and transmits data instantly for analysis and decision-making.
Data Acquisition System: An electronic system that collects, records, and stores measurements from instruments.
Automated Piezometers: Piezometers equipped with sensors and telemetry that automatically measure and transmit pore water pressure data.
Alarm Threshold: Predefined measurement limits that trigger alerts when monitoring data exceeds safe operating levels.
Performance & Risk
Excess Pore Pressure: Increased water pressure within soil pores that diminishes effective stress and soil strength.
Hydraulic Gradient: The difference in water pressure that causes seepage through soil.
Seepage Breakout: Water surfacing due to uncontrolled seepage paths.
Internal Erosion: Gradual removal of soil particles caused by seepage flow.
Piping: A tunnel-like internal erosion process that can result in dam failure.
Slope Movement: Shifting or deformation of slopes caused by instability.
Overtopping Risk: The danger of water flowing over the dam crest, which may lead to failure.
Dam Break Analysis: Modelling used to forecast flooding and impacts after dam failure.
Consequence Classification: A system that categorizes dams based on the potential consequences of failure.
ALARP: A risk principle requiring hazards to be minimized to the lowest practicable level.
Stability Analysis
Limit Equilibrium Analysis: Used to evaluate slope stability by comparing resisting and driving forces.
Critical Slip Surface: A potential failure surface that produces the lowest factor of safety.
Circular Failure: Failure where the slip surface follows a curved path.
Non-Circular Failure: Failure where the slip surface follows an irregular or composite shape.
Rapid Drawdown Condition: A situation where water levels drop quickly, leaving saturated soil with reduced stability.
Steady-State Seepage: Water flow through soil remains constant over time.
Transient Seepage: Seepage flow and pore pressures change over time.
Shear Strength Reduction: A numerical method that reduces strength parameters until failure occurs.
Finite Element Analysis: A numerical modelling method used to simulate soil behaviour, stress, and deformation.
Finite Difference Method: A numerical approach used to analyze soil behaviour using discretized grids.
Progressive Failure: Localized shear zones develop and propagate until collapse.
Residual Shear Strength: The reduced strength after significant deformation.
Peak Shear Strength: The maximum strength reached before failure.
Strain Softening: Strength decreases after peak due to continued deformation.
Strain Hardening: Strength increases with continued deformation.
Shear Band Formation: Narrow zones of intense shear deformation that can lead to failure.
Stability Terms & Industry Standards
Revegetation: Establishing vegetation to restore ecological function.
Erosion Control: Measures used to prevent soil loss.
Landform Design: Shaping reclaimed land for long-term stability.
Geochemical Stability: The ability of tailings to remain chemically stable.
Hydraulic Conductivity of Cover: The ability of a cover system to transmit water.
Unsaturated Flow: Water movement through partially filled pores.
GISTM: Global Industry Standard on Tailings Management.
CDA Dam Safety Guidelines: Canadian standards for dam design and safety.
MAC Tailings Guide: Guidance for responsible tailings management.
Water Management
Decant Tower: A structure used to collect water from the tailings pond.
Floating Decant Barge: A floating pump system used to remove water from the pond.
Return Water System: Infrastructure used to send reclaimed water back to the plant.
Water Reclaim: The recovery of water from tailings for reuse.
Pump-Back System: A system that returns seepage or runoff water back to the facility.
Spillway: A structure designed to safely release excess water.
Emergency Spillway: A secondary overflow channel used during extreme floods.
Diversion Channel: A channel built to divert surface water away from the facility.
Contact Water: Water that has interacted with tailings and may contain contaminants.
Non-Contact Water: Clean water that has not interacted with mining materials.
Dry Stack Tailings: Filtered tailings stacked and compacted with minimal free water.
Regulatory & Hydrological Terms
Accountable Executive: The senior executive responsible for tailings management and safety.
Engineer of Record: The engineer responsible for the design and performance of the facility.
Independent Tailings Review Board: External experts reviewing design and operation.
Emergency Preparedness and Response Plan: Procedures for responding to emergencies.
Failure Modes and Effects Analysis: A structured method for identifying failure mechanisms.
Quantitative Risk Assessment: Numerical evaluation of likelihood and consequences of failures.
Dam Safety Review: Periodic engineering review of dam performance.
Evaporation Losses: Water lost through evaporation.
Precipitation Input: Water entering from rainfall or snowfall.
Run-On: Surface water flowing into the facility.
Runoff: Water flowing across the surface after precipitation.
Storage Capacity: Maximum volume a facility can safely contain.
Tailings Material & Rheology
Tailings Rheology: Study of how tailings slurry flows and deforms.
Yield Stress: Minimum stress required for slurry to flow.
Slurry Density: Mass of solids and water per unit volume.
Percent Solids: Proportion of solids in slurry.
Specific Gravity of Solids: Density ratio of particles to water.
Particle Size Distribution: Distribution of particle sizes.
Cycloning: Separation of tailings into coarse and fine fractions.
Hydrocyclones: Devices that separate particles using centrifugal motion.
Coarse Sand Fraction: Larger particles used for construction or beaches.
Fine Tailings Fraction: Smaller particles remaining suspended.
Segregation: Separation of particles during transport or deposition.
Slimes: Very fine particles (clays and silts).
Closure & Reclamation
Cover System: An engineered layer placed over tailings to control water infiltration and oxygen entry.
Dry Cover: Soil cover isolating tailings from the atmosphere.
Water Cover: Water layer maintained above tailings to limit oxidation.
Engineered Soil Cover: Multilayer system to reduce infiltration and contamination.
Store-and-Release Cover: Stores rainfall temporarily and releases it through evaporation and vegetation.
Capillary Barrier: Layered soil system restricting downward water movement.
Oxygen Flux: Rate at which oxygen moves through tailings or cover materials.
Acid Rock Drainage (ARD): Acidic water formed from sulphide oxidation.
Metal Leaching (ML): Release of dissolved metals through chemical reactions.
Neutralization Potential: Capacity to neutralize acid.
Net Acid-Generating Potential: Balance between acid generation and neutralization.
Sulphide Oxidation: Reaction producing acid and dissolved metals.
