Seepage Control of Concrete Faced Dams with respect to Surface ...

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



Content:


2

Outline• Introduction

• Design Fundamentals for CFRD / CFSGD

• Cracking of Surface Slabs

• Seepage conditions due to Cracks in

Surface Slabs

• Conclusion



Content:


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



Content:


4

Introduction

Design Fundamentals


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



Content:


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



Content:


Introduction

Design Fundamentals


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)



Content:


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


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)



Content:


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


Seepage Conditons

Conclusion



Content:


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


Seepage Conditons

Conclusion

Tendency(for 60 cm x 6 passes)



Content:


Introduction

Design Fundamentals


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)



Content:


Introduction

Design Fundamentals


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)

• ...



Content:


Introduction

Design Fundamentals


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



Content:


Introduction

Design Fundamentals


Seepage Conditons

Conclusion

13

Cracking of Surface SlabsEarthquake in Turkey



Content:


Introduction

Design Fundamentals


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



Content:


Introduction

Design Fundamentals


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...)



Content:


Introduction

Design Fundamentals


Seepage Conditons

Conclusion

16

Seepage Conditions CFRD• Dam Zoning / Foundation on Bedrock

Actual phreatic

line of seepage

Study



Content:


Introduction

Design Fundamentals


Seepage Conditons

Conclusion

17

Seepage Conditions CFRD



Content:


Introduction

Design Fundamentals


Seepage Conditons

Conclusion

18

Seepage Conditions CFSGD• CFSGD Zoning / Foundation on Alluvium

� Principle Dam Design of Case Study

Drain design



Content:


Introduction

Design Fundamentals


Seepage Conditons

Conclusion

19

Seepage Conditions CFSGD



Content:


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


Seepage Conditons

Conclusion



Content:


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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Seepage Control of Concrete Faced Dams with respect to Surface ...

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