Min-North and RESEM seminar, Oulu Dam safety assessment via modelling and surveillance 2017-09-21 Roger Knutsson Ph.D. Student, Soil Mechanics [email protected]
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Min-North and RESEM seminar, Oulu
Dam safety assessmentvia modelling and surveillance
2017-09-21
Roger KnutssonPh.D. Student, Soil Mechanics
Motivation
• Continuous dam safety assessment – Why?
• Tailings dams - “Living” structures
Dam heightening
Active deposition
Fluctuating waterlevels
Examples:
Effect on Drainage? Deformations? Stability?
Motivation
FROZEN TAILINGSTHAWED TAILINGS
DEP
TH
NEW
• Continuous dam safety assessment – Why?
• Tailings dams - “Living” structures
– Concerns in cold climate?
Motivation
• Continuous dam safety assessment – Why?
• Tailings dams - “Living” structures
– Concerns in cold climate?
Raised tailings surface(deposition)
Zero-isotherm
No deposition
Frozen Frozen Frozen
Frozen
Frozen
Frozen
Generation of man-made permafrost due to tailings deposition.
• While frozen – Stiff, impermeable layers affecting drainage etc.
• When (if) thawing – Excess pore water pressure and settlements affecting the dam stability (-)
Effect on Drainage? Deformations? Stability?
AITIK TAILINGS FACILITYGällivare, Sweden
~13km2
Boliden AB,Copper Mine
Modelling
Height difference 18m
+340
+360
+380
+400
+320
0-50-100-150-200-250-300-350 50 100
TAILINGS(DEPOSITED)
Inclinometer
• FE-model (PLAXIS 2D)– Stability (Factor of Safety)
– Deformations, consolidation etc.
• Staged construction model– Construction activities 2007-2013
– Planned constructions (10 years)
• Geotechnical investigations– CPT, Laboratory work
– Soil parameters for input
2007
2013
SoilTest
(simulation)
Triaxial LAB
19-20
19-20
21-22
13-14
16-17
14-1515-16
19-2020-2121-22
22-23
23-24
17-18
18-1920-21
• Stability (Factor of Safety)– To maintain safety with time :
– Rockfill berms on downstream slope
– Support plan
Modelling (output)
What does it say about dam behavior?
Deformations or not?
+340
+360
+380
+400
+320
0-50-100-150-200-250-300-350 50 100
TAILINGS(DEPOSITED)
Inclinometer
Model
Field
2007-2013
Triaxial:Oedometer:
Oedometer Test
• Deformations– Comparison to inclinometer data
– Strong agreement
• Now we have a model/method thatcan be used both for stability AND deformation predictions.
Modelling (output)
+340
+360
+380
+400
+320
0-50-100-150-200-250-300-350 50 100
TAILINGS(DEPOSITED)
Inclinometer
2007-2013
~5mm/year
Horizontal deformationsDam E-F, Cross-section 62+315
Surface measurements by remote sensing?
Inclinometers at site
Inclinometers at site
Possibilities with RESEM:
Remote sensing as complement to field measurements?Surface movements
(Horizontal & Vertical)
“Real-time” dam safety assessment?Measurements linked to anticipated
values (via simulations) Stability assessment
Thank you!
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