Future Tailings Project-A GEC Initiative-15-09-16-Short ... · • The Future Tailings Project is a new initiative by the GEC ... • Scale-up of tailings dewatering technologies

| Geotechnical Engineering Centre

FUTURE TAILINGS PROJECTA GEC INITIATIVE

15 September 2016, UQ

ProfessorDavidWilliamsDirector,GeotechnicalEngineeringCentre

TheUniversityofQueensland,Brisbane,AustraliaEmail:D.Williams@uq.edu.au

Website: http://geotechnical.civil.uq.edu.au

CRICOS Provider No 00025B

Reported Tailings Dam Failures and Causes – Number/10-Year Interval

Little reporting of incidents Better reporting of incidents

CRICOS Provider No 00025B 2

Failure Causes vs. Tailings Dam Type

TSF Incidents, Normalised to Tailings Production Rate

Little reporting of incidents Better reporting of incidents

TSF Incidents vs. Travel Distance of Released Tailings and Water

CRICOS Provider No 00025B 5Tailings and water released from Samarco travelled 600 km to ocean in 10 days!

Ongoing Tailings Dam Failures

• 2 to 4 tailings dam failures per year, not all of which we hear about, as tailings volumes and dam heights, and hence risks, escalate

• Focus is on those that occur in developed countries (e.g. Mount Polley in Canada on 4 August 2014) or that involve global mining companies (e.g. Samarco [BHP Billiton/Vale joint ownership] in Brazil on 6 November 2015)

• Mount Polley:– https://www.youtube.com/watch?v=VYYwzAvQIF8

• Samarco:– http://blogs.agu.org/landslideblog/2016/03/27/samarco-tailings-

dam-failure-1/– https://www.youtube.com/watch?v=F5hsNj6u-mA

Mount Polley – Before and After

BeforeAfter

Mount Polley –Before and After

Mount Polley Tailings Dam Failure, Investigation and Repair• 40 m high dam, with 2.3 m water freeboard• Water and slimes against dam over long weekend –

failure was at 3:45am on Monday 4 August 2014• Failure on soft clay foundation, leading to overtopping and

erosion ~10 Mm3 of water & ~4.5 Mm3 of tailings released• Shares in Imperial Metals Corp lost 46% (CAD0.65B

~AUD0.65B) immediately after failure• Market capitalisation » Anticipated cost of repairs and

compensation• Repair at same location as failure (more was known about

this location following failure investigations)• Tailings deposition resumed within 12 months

Mount Polley TSF Failure4 August 2014

CRICOS Provider No 00025B 11Failure on a soft glacial clay foundation layer, leading to overtopping and erosion

Financial Impact of Mount Polley Tailings Dam Failure, and Repair

Repair at same location, allowing resumption within 12 months

Share price

Temporary containment New set-back embankment raise

Samarco Tailings Dam Failure and Investigation• 110 m high Fundão Dam, rising at up to 35 m/year!• Nearby mine blasts at 1pm, tremor felt at Germano Plant

at 2:15pm on 5 November 2015 (Mw = 1.8 to 2.6)• Stepped left abutment collapsed at 3:45pm, flow

overtopping Santarem Dam, inundating Bento Rodriguez• ~32 Mm3 released, killing 19, reaching Atlantic 600 km

downstream in 10 days• Shares:

– 50% owner BHP Billiton lost 25% (~AUD29B) immediately after failure, c.f. value of Samarco to BHP of ~AUD1B

– 50% owner Vale lost 32% (~25B Reais ~AUD10B)

2007 Operations Manual –Requirement for a 200 m Sand Beach

Some Early Warnings of Potential for Failure of Fundão Dam

Piping at downstream slopeof Dyke 1, 13 April 2009

Seepage, cracking and slumpingat left abutment on 15 November 2013

Cracks on dam crest and saturation at toe on 27 August 2014

Sand (a), Remoulded Slimes (b) and Intact Slimes (c)

Before (a) and After (b) Failure of Fundão Dam

Before and After Failure of Fundão Dam

Financial Impact of Samarco Tailings Dam Failure

Samarco Tailings Dam Failure and Investigation• BHP Billiton and Vale are covering Samarco's working

capital and repair and relief work• Samarco is no longer able to cover its debt repayments• Claim against Samarco/BHP Billiton/Vale:

– Brazilian Government sought 20B Reais (~USD8B or ~AUD10.5B) in clean-up costs and damages

– 2 March 2016: Samarco, BHP Billiton and Vale agree to pay USD3B (~AUD4B) over 15 years

– 1 July 2016: Brazilian Superior Court reinstated 20B Reais claim

– Samarco, BHP Billiton and Vale appealing• Animation:

– http://fundaoinvestigation.com/demonstrative-animation/

Future Tailings Project

• The Geotechnical Engineering Centre (GEC) at The University of Queensland (UQ) is focused on adding value to mining industry partners through applied project work

• The Future Tailings Project is a new initiative by the GEC with the integrated aims of:– Preserving the mining industry’s future “Social Licence to Operate”– Negating the risk of tailings dam failures – They are preventable

and should not happen!– Optimising tailings dewatering, transport, deposition, water

recovery, densification and strengthening– Facilitating cost-effective and functional tailings closure– Training – Researchers, Masters and Industry courses

• The focus will be on project work at partnering mines in Australia and Chile, and elsewhere

Future Tailings Project

• Project Duration:– 5 years in the first instance – 2016/17 to 2021/22

• Funding level sought:– Total of the order of AUD1-2 million/year, covering laboratory and

field projects, training, travel, and reporting to industry partners• Funding opportunities:

– Direct funding by industry partners for review of immediate tailings issues, to avoid unintended, costly consequences

– Grant applications to support intermediate and longer-term issues:• By UQ GEC for Australian Research Council (ARC) Linkage

Program funding, with industry and UQ support• By AguaMarina for Chilean Economic Development Agency

(CORFO), with industry and university support

Future Tailings Project – Some Industry Issues

ISSUE POSSIBLE PROJECT WORKCommon:• Scale-up of tailings dewatering technologies • Case studies and reviews• Facilitating tailings closure • Aims, function and cost-effectiveness• Training of tailings management personnel • Research, Masters and Industry coursesAustralia:• Clay mineral-rich coal tailings • Agglomeration and filtering• Co-disposal of coal tailings and coarse • Achieving filtered tailings• Densifying red mud • Rate of rise, cycling and farming• Facilitating upstream raises • Beaching, dewatering, strengthening• Preserving tailings minerals in-pit • Closure vs. removal, chemistryChile:• Seepage in populated/temperate Central Chile • Tracing surface/ground water flows and quality• Stability of cycloned sand dams • Seismic, drainage and potential for piping• Stabilising tailings in dry Northern Chile • Need for dust suppression• Bioleaching of tailings for minerals • Bench-scale and field trials• Bacterial dust mitigation and sealing • Field trials of demonstrated technology

The Future Tailings Project – Personnel

NAME POSITION EXPERTISEProf David Williams UQ GEC Director

Project Leader

Geotechnical aspects of tailings dams, tailings management and closure

Dr Pamela Chávez C. CEO AguaMarina, Antofagasta, Chile

Dust control, bioleaching and bio-corrosion aspects of tailings

Dr Harald Hofmann UQ GEC Geochemistry and hydrogeological aspects of tailings

Dr Denys Villa Gomez UQ GEC Geochemistry and metal recovery aspects of tailings

Dr Chenming Zhang UQ GEC Tailings settling, consolidation and desiccation

Dr Marcelo Llano Serna UQ GEC Tailings and tailings water run-out analysis

tbc Chilean University(ies) Seismic design

Future Tailings Project – TrainingNAME TRAINING TOPIC

Hernan Cifuentes UQ GEC PhD Integrated tailings management and closure, including Triple Bottom Line

Shriful Islam UQ GEC PhD Settling, consolidation and desiccation of tailings to optimise deposition layer thickness and cycling

Felipe Herrera UQ GEC MPhil Field settling, consolidation and desiccation of tailings

Matthew Flanagan UQ GEC undergraduate

Settling, consolidation and desiccation of tailings

Various UQ and Chilean postgraduates Various projectsVarious UQ and Chilean undergraduates Various mine-based projects, during

vacations, undergraduate theses and exchanges between Australia and Chile

Tailings Continuum(adapted from Davies and Rice, 2004)

26CRICOS Provider No 00025BOptimum for disposal to a surface TSF is likely to be thickened, otherwise filtered

Consistency of Thickened, Centrifuged and Filtered Tailings

High density slurry

Filtered (dry cake)Centrifuged (wet cake)

Low slump pasteHigh slump paste

27Filtration gives tailings more “structure” than thickening or centrifuging

Optimising Tailings Management

• Divert clean rainfall runoff around TSF• Discharge tailings as thick as can cost-effectively be

managed (paste only in-pit or underground via gravity)• Spigot thickened tailings in thin layers and cycle

deposition between a number of cells• Maintaining a small decant pond to maximise dewatering,

desiccation, densification and strengthening of tailings, provided dust can be controlled

• Ideally, having separate evaporation or tailings water storage ponds

• Scale-up robust filtration technologies, including belt press, plate and frame and screw press

Future Tailings Project – Facilities and Methods – Slurry Consolidometer

Purpose-built slurry consolidometer:• Diameter 150 mm• Height 410 mm• Instrumented with top

and base load cells, and pore water pressure transducers

Enabling tailings slurry specimens to be placed in layers, allowed to settle and then consolidated under up to 500 kPa (~60 m of tailings self-weight)

Simulating build-up of tailings from a slurry state

Example Slurry Consolidometer Result

Future Tailings Project – Facilities and Methods – Column Testing

Purpose-built settling, consolidation and desiccation column for use in lab and field (with a weather station):• Diameter 200 mm• Height 1.4 m, in sections for ease of

specimen preparation and post-test sampling

• Instrumented with moisture, salinity, temperature and suction sensors

• Water balance monitored• Tested from a slurry placed in layers

Calibrated from lab to field to full-scale

For optimising deposition layer thickness and cycle time, and hence TSF footprint for a given tailings production

200 mm

400 mm

Future Tailings Project – Facilities and Methods – Column Testing

Column Testing with Weather Station on Roof at UQ

Column set up with weather station on roof at UQ, transferable to site

Automated

Real-time data collection, processing and delivery

Example Desiccation Column Test Result

Future Tailings Project – Facilities and Methods – Drying & Filtration

SWCC device for simulating drying of tailings under applied pressure (suction):• Diameter 75 mm• Height 25 mm• Measures moisture vs. suction

Filtration cell:• Diameter 75 mm• Height 100 mm• Up to 700 kPa applied pressure

Example of Laboratory and Field SWCC Test Results

0.1 1 10 100 1000 10000 100000 1000000MATRIC SUCTION (kPa)

Average drying SWCC for TSF 1 tailingsAverage re-wetting SWCC for TSF 1 tailiungsField data to 0.2 m depthField data below 0.2 m depth

Field regime

Tempe re-drying

Tempe re-wetting

Laboratory regime

Future Tailings Project – Facilities and Methods – Field Shear Vane

Purpose-built field shear vane:• Vane diameter 130 mm• Vane height 65 mm• Three rod lengths of 1 m• Inner rod rotated inside an outer

sleeve to avoid rod shear• Torque applied by hand and

recorded against rotation• “Peak” and “remoulded” vane

shear strengths measured

Correlated against Cone Penetration Test cone resistance, and laboratory characterisation results

Schematic Shear Strength Profiles with Depth

Self-weight + Amphirol +2 m Fill+ Desiccation

Desiccation and fill are most effective for consolidation and strengthening

38CRICOS Provider No 00025B

Future Tailings Project – Field Sampling & Trials• Tailings beach measurements and sampling for:

– Beach profile– Physical, chemical and biological characterisation testing– Particle sorting– Vane shear profiles with depth down beach– Slurry consolidometer testing– Settling, consolidation and desiccation testing

• Accelerated bacterial dust mitigation and sealing for closure

• Development of closure criteria:– Erosion and seepage control– Contamination potential and lag time– Need for and purpose of any covers

Future Tailings Project – Expected Outcomes• Integrated, robust and sustainable approaches to tailings

management and closure– Preserving the mining industry’s future “Social Licence to Operate”– Negating the risk of tailings dam failures– Coping with declining ore grades – increasing grinding and tailings

tonnages vs. heap and bioleaching– Improving tailings filtration scale-up predictability and outcomes– Offsetting filtration costs against water recovery and closure– Optimising tailings dewatering, transport, deposition, water

recovery, densification and strengthening– Facilitating cost-effective and functional tailings closure– Training:

• Research• Masters and Industry courses

Future Tailings Project-A GEC Initiative-15-09-16-Short ... · • The Future Tailings Project is a new initiative by the GEC ... • Scale-up of tailings dewatering technologies

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