seepage control of concrete faced dams with respect to surface
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Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Prepared by:
Ronald Haselsteiner (EnerjiSA, Turkey)
Burcu Ersoy (Fichtner, Turkey)
Conference Presentation
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
2
Outline• Introduction
• Design Fundamentals for CFRD / CFSGD
• Cracking of Surface Slabs
• Seepage conditions due to Cracks in
Surface Slabs
• Conclusion
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
3
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
General InformationCountry
• Area: 779,452 km²
10 x Austria / 2 x Germany / 8 x Portugal
• Location: 3% Europe + 97% Asia
• Population: 70.6 Mio. Inhabitants
74% of population in major cities
Austria: 8.2 / Germany: 82.3 / Portugal: 10.6
• Aver. Age: 27.3 a
Austria: 42 / Germany: 41 / Portugal: 40
• Pop. density: 91 Inhabitants/km²
Austria: 100 / Germany: 229 / Portugal: 119
• Religion: 99% Muslims
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
4
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
Energy Market / HydropowerPrognosis of Energy Demand
• 2005: 160 103 GWh/a
• 2010: 242 103 GWh/a (+50%)
• 2020: 356 to 476 103 GWh/a (min +122%)
• Growth rate 8.2% in 2008 (economy 4%, pop. 1-2%)
Strategy in Hydropower Sector
• Utilization of Economically Feasible Energy Potential
(EFEP) of Hydropower
• EFEP = 125 to 188 TWh/a
• Currently, 1/3 of EFEP is utilized
• Privatization of Energy Market 2000/01
• Expected Private Investment (~ 50,000 Mio. € in 2020!)
• Thread of Energy Deficit in 2012–2015 (2020)
• Currently, 2,000 HEPP in development
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
5
Sarigüzel
CFSGD80 m
(under
construction)
Kandil
CFRD100 m
(under
construction)
Alpaslan II
CFRD100 m
(final design)
Arkun
CFSGD100 m
(under
construction)
Ankara
Istanbul
Under construction
Final design stage
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
6
Typical Cross-Section CFRD
3B
3C1B 1A
FS2B
3A
2AP
3B
3C
OR
3A
3B
3C
1A
1B
2A
2B
P
FS
Filter Zone
Rockfill (well compacted)
Rockfill
Self-Healing Fill
Protection Fill
Perimeter Zone
Cushion Zone
Plinth
Concrete Face Slab
B Bedrock
B
Literature:A) ICOLD, Concrete Face Rockfill Dams – Concepts for Design and Construction, International Committee on Large Dams, Committee on Materials for Fill Dams (Draft) (2005)
(adapted from ICOLD, 2005A)
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
7
Typical Cross-Section CFSGD
3B
3C3D
1B 1A
FS 2B
3A
2A
2C
P
B
3A
3B
3C
3D
1A
2A
2B
2C
P
FS
Filter Zone
Sand-Gravel-Fill
Sand-Gravel-Fill (dirty)1)
Rockfill
Self-Healing Fill
Perimeter Zone
Cushion Zone
Filter
Plinth
Concrete Face Slab
1B Protection Fill
1) If available or necessary for slope stability and/or seepage control
B Bedrock
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
Literature:A) R. Fell, P. MacGregor, D. Stapledon, G. Bell, Geotechnical Engineering of Dams, A. A. Balkema Publishers, Leiden London New York Philadelphia Singapore (2005)
(adapted from Fell et al., 2005A)
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
8
Sand-Gravel Fill vs. Rockfill
• Occurence: Quarry - Processing ↔ Natural deposits (alluvium)
• Seepage: Free draining1) ↔ Sand and fine particles
Simple zoning ↔ Seepage control zoning
• Shear strength: Crushed angular grains ↔ Rounded grains
High friction angle ↔ Friction angle controlled by
main components
• Stress: Sensitive, weak materials ↔ Less dependent
• Deformation: Less favourable ↔ High elasticity moduli(see next slide)
Notes:1) Considered loads and dam (seepage) conditions are not likely to allow extensive pore water pressures within the dam body.
Comparison
Aspect Rockfill Sand-Gravel↔
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
9
Sand-Gravel Fill vs. RockfillElasticity Modulus
• Well-graded material (probably)
• Higher values for SG
• Less stress dependent
� Less deformation
• Less layer height
• Number of passes 4-8
Sarigüzel Project
(min)
(max)
(mean)
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
Tendency(for 60 cm x 6 passes)
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
10
Cracking of Surface SlabsExperiences / Case Studies
• Seepage flow in CFRDs & CFSGDs
• Ita (Brazil): 1,700 l/s; H = 125 m
• Shiroro (Nigeria): 2,000 l/s; H = 125 m (� 100 l/s after sealing joints)
• Scofield (USA): 5,600 l/s; H = 40 m
• Campos Novos (Brazil): 1,400 l/s; H = 202 m (50 MPa)
• Barra Grande (Brazil): 1,300 l/s; H = 185 m
• Aguamilpa (Mexico): 200 l/s; H = 187 m
• El Cajon (Mexico): 150 l/s; H = 188 m
• Shuibuya (China): 40 l/s; H = 233 m (80-100 MPa)
• Maximum slab deformation
• Salt Spring (USA): > 1.0 % of height (dumped rockfill)
• Shuibuya (China): 0.5 % of height (double of expected)
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
11
Cracking of Surface SlabsReasons for Cracking
• Deformation cracks are of major concern
• Tension / compression cracks
• 50% of deformation during „First impoundment“
• Likelyhood of cracking for E < 50 MPa and large dams is high
• Geotechnical investigation – lack of information/data
• Design inconsistencies (Gouhou dam (!), Aguamilpa)
• Unfavourable material properties
• Construction works
• Dynamic loads - Earthquake (next slide)
• ...
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
12
Cracking of Surface SlabsDynamic Loads - Earthquake
Direct impact
• Displacement of the surface slab blocks
• Failure of joint sealing components (copper inlays)
• Deformation, displacements of filter layers (functionality, seepage control)
• Loosening of soil/rock strength
• Liquefaction (should be excluded by choice of materials for SG or RF)
Indirect impacts
• Landslides � Impulse on dam body, surface slab, shock waves,
overtopping...
• Rockfalls
• ...
• Determination of design parameters & evaluation of impact difficult
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
13
Cracking of Surface SlabsEarthquake in Turkey
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
14
Cracking of Surface SlabsEarthquake in Turkey
PGA values1st: > 0.4g2nd: 0.3g - 0.4g3rd: 0.2g - 0.3g4th: 0.2g - 0.1g5th: <0.1g
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
15
Cracking of Surface SlabsConsequences & Countermeasures
• Seepage intrusion/increase
� Pore water pressures
� Hydrodynamic soil deformation (erosion, suffusion)
� Seepage losses (electricity generation!)
� Damages & failure
� Fatalities (!) & economic/social impacts
• Rapid drawdown (if possible, stability of upstream slope)
• Addition of silty sand, flyash, bentonite...
• Joint design � More joints more flexibility
• Proper choice of the deformation parameters of different zones
• Local increase of slab thickness
• Zoning for seepage control & self-healing zone 1A
• Refurbishment measures (concrete, geomembranes...)
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
16
Seepage Conditions CFRD• Dam Zoning / Foundation on Bedrock
Actual phreatic
line of seepage
Study
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
17
Seepage Conditions CFRD
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
18
Seepage Conditions CFSGD• CFSGD Zoning / Foundation on Alluvium
� Principle Dam Design of Case Study
Drain design
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
19
Seepage Conditions CFSGD
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
20
Conclusion• Static loads � Cracking „predictable“ for the case of
reliable construction works and constant material
quality
• Dynamic loading � Cracking „hardly predictable“
(case studies? Wenchuan China 2008)
• Adaptation of zoning/design in order to control
seepage conditions in case of cracking
• Pore water pressures � Draining
• Erosion/suffusion � Filter
� Direct consequences of cracking to be controlled
Introduction
Design Fundamentals
Cracking of Surface Slabs
Seepage Conditons
Conclusion
Conference, Date, Location:
6th Conference on Dam Engineering, 15.-17.02.2011, Lisbon
Content:
Seepage Control of Concrete Faced Dams with respect to Surface Slab Cracking
21
Thank you.
βα
p
Engineering
Judgement
Engineering
Principles!A)
Reference:A) Hartford, D. (2011): Risk management in embankment dams – Geotechnical component. Session 4: Future Directions: beginnning by going back to the scientific foundations. LNEC, Portugal
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