Upload
others
View
6
Download
0
Embed Size (px)
Citation preview
| Geotechnical Engineering Centre
FUTURE TAILINGS PROJECTA GEC INITIATIVE
15 September 2016, UQ
ProfessorDavidWilliamsDirector,GeotechnicalEngineeringCentre
TheUniversityofQueensland,Brisbane,AustraliaEmail:[email protected]
Website: http://geotechnical.civil.uq.edu.au
CRICOS Provider No 00025B
| Geotechnical Engineering Centre
Reported Tailings Dam Failures and Causes – Number/10-Year Interval
Little reporting of incidents Better reporting of incidents
CRICOS Provider No 00025B 2
| Geotechnical Engineering Centre
Failure Causes vs. Tailings Dam Type
CRICOS Provider No 00025B 3
| Geotechnical Engineering Centre
TSF Incidents, Normalised to Tailings Production Rate
Little reporting of incidents Better reporting of incidents
CRICOS Provider No 00025B 4
| Geotechnical Engineering Centre
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!
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 6
| Geotechnical Engineering Centre
Mount Polley – Before and After
CRICOS Provider No 00025B
BeforeAfter
7
| Geotechnical Engineering Centre
Mount Polley –Before and After
CRICOS Provider No 00025B 8
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 9
| Geotechnical Engineering Centre
Mount Polley TSF Failure4 August 2014
CRICOS Provider No 00025B 10
| Geotechnical Engineering Centre
Mount Polley TSF Failure4 August 2014
CRICOS Provider No 00025B 11Failure on a soft glacial clay foundation layer, leading to overtopping and erosion
| Geotechnical Engineering Centre
Financial Impact of Mount Polley Tailings Dam Failure, and Repair
CRICOS Provider No 00025B
Repair at same location, allowing resumption within 12 months
Share price
Temporary containment New set-back embankment raise
12
| Geotechnical Engineering Centre
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)
CRICOS Provider No 00025B 13
| Geotechnical Engineering Centre
2007 Operations Manual –Requirement for a 200 m Sand Beach
CRICOS Provider No 00025B 14
| Geotechnical Engineering Centre
Some Early Warnings of Potential for Failure of Fundão Dam
CRICOS Provider No 00025B
Piping at downstream slopeof Dyke 1, 13 April 2009
Seepage, cracking and slumpingat left abutment on 15 November 2013
15
Cracks on dam crest and saturation at toe on 27 August 2014
| Geotechnical Engineering Centre
Sand (a), Remoulded Slimes (b) and Intact Slimes (c)
CRICOS Provider No 00025B 16
| Geotechnical Engineering Centre
Before (a) and After (b) Failure of Fundão Dam
CRICOS Provider No 00025B 17
| Geotechnical Engineering Centre
Before and After Failure of Fundão Dam
CRICOS Provider No 00025B 18
| Geotechnical Engineering Centre
Financial Impact of Samarco Tailings Dam Failure
CRICOS Provider No 00025B 19
| Geotechnical Engineering Centre
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/
CRICOS Provider No 00025B 20
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 21
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 22
| Geotechnical Engineering Centre
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
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 24
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 25
| Geotechnical Engineering Centre
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
| Geotechnical Engineering Centre
Consistency of Thickened, Centrifuged and Filtered Tailings
CRICOS Provider No 00025B
High density slurry
Filtered (dry cake)Centrifuged (wet cake)
Low slump pasteHigh slump paste
27Filtration gives tailings more “structure” than thickening or centrifuging
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 28
| Geotechnical Engineering Centre
Future Tailings Project – Facilities and Methods – Slurry Consolidometer
CRICOS Provider No 00025B
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
29
| Geotechnical Engineering Centre
Example Slurry Consolidometer Result
CRICOS Provider No 00025B 30
| Geotechnical Engineering Centre
Future Tailings Project – Facilities and Methods – Column Testing
CRICOS Provider No 00025B
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
31
200 mm
400 mm
400 mm
400 mm
| Geotechnical Engineering Centre
Future Tailings Project – Facilities and Methods – Column Testing
CRICOS Provider No 00025B 32
| Geotechnical Engineering Centre
Column Testing with Weather Station on Roof at UQ
CRICOS Provider No 00025B
Column set up with weather station on roof at UQ, transferable to site
Automated
Real-time data collection, processing and delivery
33
| Geotechnical Engineering Centre
Example Desiccation Column Test Result
CRICOS Provider No 00025B 34
| Geotechnical Engineering Centre
Future Tailings Project – Facilities and Methods – Drying & Filtration
CRICOS Provider No 00025B
SWCC device for simulating drying of tailings under applied pressure (suction):• Diameter 75 mm• Height 25 mm• Measures moisture vs. suction
35
Filtration cell:• Diameter 75 mm• Height 100 mm• Up to 700 kPa applied pressure
| Geotechnical Engineering Centre
Example of Laboratory and Field SWCC Test Results
CRICOS Provider No 00025B
0
10
20
30
40
50
60
0.1 1 10 100 1000 10000 100000 1000000MATRIC SUCTION (kPa)
GR
AV.
MO
ISTU
RE
CO
NTE
NT
(%)
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
36
| Geotechnical Engineering Centre
Future Tailings Project – Facilities and Methods – Field Shear Vane
CRICOS Provider No 00025B
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
37
| Geotechnical Engineering Centre
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
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 39
| Geotechnical Engineering Centre
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
CRICOS Provider No 00025B 40