A. Marulanda. Recent incidents in high CFR dams

RECENT INCIDENTS IN HIGH CFRD DAMSRECENT INCIDENTS IN HIGH CFRD DAMS

Sherard & Cooke 1985 CFRDSherard & Cooke 1985 CFRD ASCE Symposium:ASCE Symposium:““The CFRD is an appropriate type in the future for the very highest The CFRD is an appropriate type in the future for the very highest dams. For a 300m high CFRD constructed of most rock types, dams. For a 300m high CFRD constructed of most rock types, acceptable performance can be predicted, based on reasonable acceptable performance can be predicted, based on reasonable extrapolation of measurements on existing dams”extrapolation of measurements on existing dams”

Sherard & Cooke 1985 CFRDSherard & Cooke 1985 CFRD ASCE Symposium:ASCE Symposium:““For CFRD with compacted rockfill and a compacted upstream For CFRD with compacted rockfill and a compacted upstream face, the thickness increment was decreased to 0.003H, and even to face, the thickness increment was decreased to 0.003H, and even to 0.002H or less. These slabs have given satisfactory performance, an 0.002H or less. These slabs have given satisfactory performance, an thEre is a current general trend toward thinner slabs.”thEre is a current general trend toward thinner slabs.”

Sherard , 1985 CFRD ASCE Symposium:Sherard , 1985 CFRD ASCE Symposium:“…“….The writer believes that it is likely that the not distance future .The writer believes that it is likely that the not distance future evolution of the CFRD could arrive at a constant slab thickness of evolution of the CFRD could arrive at a constant slab thickness of the order of 8 to 10 inches, even for high dams, with simpler and the order of 8 to 10 inches, even for high dams, with simpler and more economical joint seals.””more economical joint seals.””

Cooke 2000 Beijing Symposium:Cooke 2000 Beijing Symposium:““There has since been no experience to change that conclusion. There has since been no experience to change that conclusion. There have been leakage incidents, and for the CFRD “acceptable There have been leakage incidents, and for the CFRD “acceptable performance” can include a leakage incident.”performance” can include a leakage incident.”““Experience with existing dams has not identified areas in design Experience with existing dams has not identified areas in design which require significant change in design practice for the next which require significant change in design practice for the next generation of higher dams, 190-230m”generation of higher dams, 190-230m”

General trends of recent high dams:

•About 190 m high•Without anti-spalling reinforcement along compression joints•Thickness reduction of the concrete slab•In low-seismicity areas, outer slopes increased to 1.3 to 1 and 1.25 to 1.•Use of an extruded concrete curb as surface protection before placing the slab

Recent events:

•Barra Grande & Campos Novos in Brazil and Mohale in South Africa.•Significant cracking of the central portion of the dam after first filling.•Rockfill: basalt. Highly compressive, modules around 45 to 50 MPa•Used curb as surface protection.•Shape factors (A/H2) around 3•China reported that similar cracks have occurred after years of continuing settlements with time

ANTAMINA DAMANTAMINA DAM

EL.3911

EL.4015

EL.4116

EL.3906

EL.3935EL.3921 Starter Water Dam

High Tailings Dam

Antamina CFRDAntamina CFRD

CONCRETE FACE SLIP FORMING

TA

ILIN

GS

STA

RT

ER

DA

M -

PER

Ú

TA

ILIN

GS

STA

RT

ER

DA

M -

PER

Ú

VERTICAL AND PERIMETER JOINTS

ANTAMINA DAMANTAMINA DAM– CURB CRACKING– CURB CRACKING

ANTAMINA DAMANTAMINA DAM– CURB FAILURE– CURB FAILURE

BARRA GRANDE DAMBARRA GRANDE DAMSECOND STAGE SLAB PLACEMENTSECOND STAGE SLAB PLACEMENT

CAMPOS NOVOS DAM - UPSTREAM FACECAMPOS NOVOS DAM - UPSTREAM FACE

CAMPOS NOVOS DAMCAMPOS NOVOS DAMSLAB CRACKING – 2ND MOVEMENTSLAB CRACKING – 2ND MOVEMENT

CAMPOS NOVOS DAMCAMPOS NOVOS DAM

L20 L19

8 cm

MASTER TOP

COPPER WATERSTOP

L20 REINFORCEMENT L19 REINFORCEMENT

RUBBER JOINT

15 cm 15 cm

PRESA BARRA GRANDEPRESA BARRA GRANDEREPAIR WORKSREPAIR WORKS

BARRA GRANDE DAMBARRA GRANDE DAM

CAMPOS NOVOS DAM - SLAB 17 REPAIRCAMPOS NOVOS DAM - SLAB 17 REPAIR

MOHALEMOHALE DAM DAM

SOGAMOSO BARRA GRANDEAGUAMILPA

TIANGSHENQIAOPOZ DO AREIA

SALVAJ INAPORCE III

MACHADINHO

CAJ ONGOLILLAS

MOHALE

YESCACAMPOS NOVOS

ALTO ANCHICAYÁ

CETHANA

SEGREDO

XINGÓ

ITA

SETTLEMENTS DURING CONSTRUCTIONSETTLEMENTS DURING CONSTRUCTION

0

500

1000

1500

2000

2500

3000

3500

4000

0 1 2 3 4 5 6 7 8Shape Factor (A/H²)

Max

. Fill

Set

tlem

ent [

mm

]

GolillasSalvajina

Kurtun

Barra Grande

Campos Novos

Aguamilpa

Segredo

Foz AreiaTiangshenqiao

Xingo

Tiangshenqiao (long term)

Cajón

FILL MODULUSFILL MODULUS

0

50

100

150

200

250

300

350

400

450

0 1 2 3 4 5 6 7 8

Shape Factor A/H²

Fill

Ver

tical

Mod

ulus

-MP

a

Golillas

Salvajina

Aguamilpa

Cajón

Foz AreiaMohale

Barra Grande

Campos Novos

Kurtun

Alto Anchicayá

SegredoMachadinho

ItáXingó

Tiangshenqiao

TORUL DAMTORUL DAM

FACE SLAB DEFORMATIONFACE SLAB DEFORMATION

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7 8

Shape Factor (A/H²)

Face

Sla

b N

orm

al d

efle

ctio

n (D

/H) X

103

GolillasAlto Anchicaya

Cethana

Salvajina

Campos Novos

Barra Grande

Aguamilpa

Segredo

Foz Areia

Tiangshenquiao

Machadinho

Xingo

Ita

Mohale

Kurtun

Cajón

Preliminary Analyses

•Time and way of construction of the concrete face is important. Largest stresses are caused by associated settlements due to own weight.

- Kurtun (Turkey 140m). Delayed slab construction

•Water load imposes additional loading that can be decisive in cracking the slab if the accumulated stresses that exist in the dam by previous settlements are large enough and the geometry of the canyon makes a big difference.

- Foz Areia vs. BG & CN Dams (Wide and narrow canyons)

RECENT CHANGES OF THE RECENT CHANGES OF THE CFRD ICOLD BULLETINCFRD ICOLD BULLETIN

““More recently, structural cracks concentrated along central More recently, structural cracks concentrated along central vertical joints of very high dams in narrow canyons have been vertical joints of very high dams in narrow canyons have been observed. The cracks appear to be associated with rockfills of observed. The cracks appear to be associated with rockfills of higher compressibility (Ev less than 40Mpa),with heights greater higher compressibility (Ev less than 40Mpa),with heights greater than 140m, and canyons with a shape factor (Area of face slab than 140m, and canyons with a shape factor (Area of face slab divided by maximum dam height, squared, Pinto 2003) less than 3. divided by maximum dam height, squared, Pinto 2003) less than 3. These cracks have appeared upon reservoir filling and only after These cracks have appeared upon reservoir filling and only after more than 85% of maximum level has been reached. These cracks more than 85% of maximum level has been reached. These cracks are identified as shear cracks, that can be rather spectacular as are identified as shear cracks, that can be rather spectacular as pieces of concrete detach from the face. Once they occur, if pieces of concrete detach from the face. Once they occur, if reservoir lowering is not possible, the only solution for reducing reservoir lowering is not possible, the only solution for reducing leakage is to dump finer material on top of the affected area.leakage is to dump finer material on top of the affected area.””

Recent Changes to CFRD – ICOLD BulletinRecent Changes to CFRD – ICOLD Bulletin

Recent Changes to CFRD – ICOLD BulletinRecent Changes to CFRD – ICOLD Bulletin

Structural cracks concentrated along central vertical jointsStructural cracks concentrated along central vertical joints

Ev<40 MPa

A/H2

85% of the

maximum level

8Page 6-8

““New paragraph for Vertical Compression Joint:New paragraph for Vertical Compression Joint:

““For high dams in narrow canyons some designers have added For high dams in narrow canyons some designers have added compressible material along vertical compression joints. Aguamilpa compressible material along vertical compression joints. Aguamilpa and El Cajon in Mexico have added compressible timber in and El Cajon in Mexico have added compressible timber in alternate pairs of vertical compression joints. It follows the same alternate pairs of vertical compression joints. It follows the same principle described in 5.6 for the perimeter joint, but contrary to the principle described in 5.6 for the perimeter joint, but contrary to the concept of being necessary only for the construction period, in the concept of being necessary only for the construction period, in the case of vertical compression joints it is intended to avoid spalling of case of vertical compression joints it is intended to avoid spalling of the concrete because of water loadthe concrete because of water load.”.”

Recent Changes to CFRD – ICOLD Bulletin Recent Changes to CFRD – ICOLD Bulletin

PRESA EL CAJONPRESA EL CAJON

JUNTAS TIPO 3 Y 4 - COMPRESIÓNJUNTAS TIPO 3 Y 4 - COMPRESIÓN

SALVAJINA DAM - JointsSALVAJINA DAM - Joints

Tension Joints Compression Joints

Additional considerations at Karahnjukar dam, (190m high) under Additional considerations at Karahnjukar dam, (190m high) under construction in Iceland, in recognition of the high compressive construction in Iceland, in recognition of the high compressive stresses that can occur between the central face slabs:stresses that can occur between the central face slabs:

• • Bituminous fiber sheet joint filler, 15 mm thick, in the joints Bituminous fiber sheet joint filler, 15 mm thick, in the joints of the 10 central face slabs, andof the 10 central face slabs, and• • Anti-spalling reinforcement in the compression joints.Anti-spalling reinforcement in the compression joints.• • Central face slab thickening from e = 0.3 + 0.002H to e = Central face slab thickening from e = 0.3 + 0.002H to e = 0.4 + 0.002H. The face slab thickening occurs only above 0.4 + 0.002H. The face slab thickening occurs only above

the first stage face slabs already constructed. Reinforcement the first stage face slabs already constructed. Reinforcement is about 0.5% both ways in the thickened face slabs.is about 0.5% both ways in the thickened face slabs.


•““Convex face deformation due to high fill deformations can Convex face deformation due to high fill deformations can accentuate compression stresses along these joints especially in accentuate compression stresses along these joints especially in case of narrow valleys, making the feature of this compressible filler case of narrow valleys, making the feature of this compressible filler even more important and probably necessary along all compression even more important and probably necessary along all compression joints.joints.””

•““For high dams in narrow canyons anti-spalling reinforcement is For high dams in narrow canyons anti-spalling reinforcement is advisable for all vertical joints. At the center of the dam high advisable for all vertical joints. At the center of the dam high compression stresses require the use of this reinforcement. For these compression stresses require the use of this reinforcement. For these dams reduction in slab thickness has the additional consequence of dams reduction in slab thickness has the additional consequence of reducing reinforcement if steel ratio is maintained constant. reducing reinforcement if steel ratio is maintained constant. Therefore detail consideration must be given to slab thickness as Therefore detail consideration must be given to slab thickness as well as steel ratio for these high dams with low modulus rockfill in well as steel ratio for these high dams with low modulus rockfill in narrow canyons.”narrow canyons.”


On-going Analyses: On-going Analyses:

-Detailed analyses including staged Detailed analyses including staged construction and reservoir construction and reservoir impoundment.impoundment.

-Detailed interaction between rockfill Detailed interaction between rockfill and concrete slab.and concrete slab.

- Detailed modeling of the joint - Detailed modeling of the joint behaviorbehavior

A. Marulanda. Recent incidents in high CFR dams

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