foundation tratment

7/29/2019 foundation tratment

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Foundation TreatmentMeasures for Dams

Located onKarst Foundations


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Educational ObjectivesOn completion of this course, students will:

This course will provide the student with an overview of

foundation treatments for dams constructed on karst foun-

dations. For this course the Kavar Dam in Iran was the

example where an unusual combination of a surface mem-

brane, coupled with a gypsum surcharge and other seepage

control measures, were planned to seal a highly karstic

foundation.

IntroductionKarsticity occurs as a result of a progressive disolutioning

of carbonate rocks exposed to water and carbon dioxide. In

pure water, at 25oC, the maximum possible concentration

of dissolved calcium carbonate is in the range of 14 mg/L

(Fookes and Hawkins, 1988). However, in the presence of

dissolved carbon dioxide, maximum concentrations increase

dramatically, accounting for the fact that seepage owing

from karst formations often contains up to 400 mg/L of

calcium carbonate ( James and Fitzpatrick, 1988). Therefore,

a karstic formation implies the presence of a network of

solutioned, often highly permeable, discontinuities which

are, by denition, connected to the surface so that the free

carbon dioxide necessary to allow the solutioning process to

continue is available. This fact means that Karst founda-

tions are usually associated with highly deformed, complex,

rock masses that have pervious windows extending directly

to the foundation surface.

The diculties involved in constructing a dam on a

karstic foundation were rst documented at Hales Bar damthat was built by private interests on the Tennessee River

between 1905 and 1913. Although the existence of cavernous

rock in the limestone foundation was postulated, geological

theory at the time suggested that cave formation occurred

only above the water table. (T.V.A. Technical Report No.

22, 1949). Therefore, very little foundation treatment was

performed and, following construction, leakage under the

dam of up to 48 m3/s was measured. Various remedial works

projects were carried out at the site over the 60 years that

it was in operation until, in 1968, the dam was demolished.

In the years following the construction of the Hales bar

dam the eects of solutioning have had adverse impacts on

both reservoir water tightness and the structural integrity

of many dams. Although there are few documented struc-

tural failures attributed to sinkhole collapse in karst ter-

rain, there are numerous examples of problems associated

with reservoir lling. For example, at the Lar dam in Iran

(Uromeihy, 2000) it was not possible to impound to full sup-

ply level due to foundation leakage that reached two-thirds

of the total river ow. A remedial grouting program, per-

formed between 1985 and 1990, was only partially success-

ful in reducing seepage and, to date, the reservoir remains

partially lled. In the case of the Anchor Dam constructed

in 1960, (Fig. 1), an extensive system of sinkholes and faults

have prevented any permanent storage of water, despite

numerous remedial sealing attempts. (ww w.usbr.gov/cdams/

dams)

As a result of experience gained from such dams,

techniques have been developed to successfully treat even

seriously karstic foundations. This course describes current

practice for the design of dams on karst terrain as well assome unique seepage control measures that are planned to

mitigate risks associated with a highly karstic limestone

foundation in Iran. These measures include the use of an

Foundation Treatment Measures for

Dams Located on Karst Foundations

1. Understand the diculties of constructing

a dam on a karstic foundation.

2. Identify methods to treat karstic foundationsfor the construction of a dam.

3. Understand grouting techniques and other seepage

control measures for karstic foundations.

4. Understand the eects of solutioning on reservoirwater tightness and the structural integrity of dams.


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Figure 1 The Anchor Dam Wyoming USA

Figure 2 Effect of Multiple Line Grouting on the Median Post Impoundment

Seepage Reported for Some Selected Precedent Dams (ref. Table 1)

600

300

200

MedianPos

tImpoundmentSeepage(l/sec)

100

0

0

Number of Grout Lines

1 2 3 4

400

400

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engineered soluble ll and a surcial shot-

crete membrane to seal the foundation

surface.

CurrentPractice

The key to any successful construction

on a karst foundation is a thorough un-

derstanding of the nature of the problemsthat must be treated. In the rst half of

the 20th century, dams such as the Hales

Bar, Wolf Creek, Mosul, and Great Falls

were constructed on karstic foundations without adequate

foundation explorations. All experienced either foundation

leakage or piping problems. More recently, the problems

at the Lar dam are likely related, at least in part, to an in-

adequate understanding of the depth of karst prior to the

commencement of construction.

On the other hand, if exploration and foundation treat-

ment measures are carried out thoroughly, even a highlykarstic foundation can be successfully treated. For example,

advanced karst foundations beneath the 90 to 100 m high

Pueblo Viejo and Punt Dal Gall dams were successfully

treated such that post-impoundment seepage has only been

25 and 50 l/sec respectively.

In broad terms, modern practice for the successful treat-

ment of karstic foundations requires a means of reducing

the amount of seepage, techniques to prevent dissolution

of soluble minerals that may be present in the foundation,

and methods to ensure that the foundation has adequate

capacity to resist the post impoundment loadings without

excessive settlement.

Improving Deformability

Commonly applied techniques for improving the deform-

ability and stability of karst foundation rocks include exca-

vation/mucking of solution cavities followed by lling with

a sand and gravel slurry, concrete and/or compaction grout-

ing. For example, at the 21 dams that the Tennessee Valley

Authority (TVA) has constructed on carbonate foundations,

Soderberg (1988) notes that foundation treatment typically

includes consolidation grouting to ensure adequate bearing

strength and to minimize settlements. Solutioned areas, in

otherwise sound rock, are then mucked or excavated and

lled with concrete.

More recently, compaction grouting has been used to

treat karst features. This technique involves the injection

of low-slump soil/cement grout to displace and/or compress

the surrounding soils for greater strength (Fischer and

Fischer, 1995). This typically results in hydraulic fractur-

ing, extrusion and consolidation of clayey llings within

the sinkholes increasing strength, and resistance to seep-age stresses. Welsh (1988) and Zuomei and Pinshou (1988)

describe the use of compaction grouting to rectify sinkholes

and caves lled with clay llings and to build a seepage

resistant barrier in Karst terrain for the

Wujiangdu Hydroelectric Project in China.

Reducing the Potential for Dissolution of Soluble

Minerals

The most commonly occurring soluble rock

minerals are calcium carbonate (limestone)

gypsum, anhydrite and halite. In general,mitigation of the risk of solutioning in a

foundation containing such minerals re-

quires reducing the volume of seepage and

seepage gradients. This, traditionally, had been accom-

plished on the basis of precedent practice. An analytical

framework for assessing the solutioning potential of various

forms of soluble rock minerals was rst presented by James

and Lupton (1978). James and Kilpatrick (1980) used these

solutions to study seepage control measures for dam con-

structed on foundations containing the soluble rocks. They

concluded that grouting, or the provision of an upstreamimpervious blanket, can control the solutioning of calcium

carbonate rock. For foundations containing gypsum, con-

ventional (sulphate resistant) cement curtain grouting was

recommended. Mineral deposits such as anhydrite were

found to require a more ecient cuto, such as plastic con-

crete wall in combination with measures such as upstream

blankets or other techniques designed to reduce seepage

velocities. They recommended that halite, in its massive

form, be avoided. However, it is of note that an active brine

injection system has been used to treat foundations contain-

ing hal ite mineral deposits (Pokrovskii, 1994).

Grouting

For well developed karst foundations, a sulphate resistant

multiple line grout curtain, with provisions to allow future

grouting, is typically used to reduce seepage losses. For

lower head dams, or for dams on less well developed karst,

single or double line curtains are often used. However,

all karstic foundations should be treated with caution. As

shown on Table 1, very high seepages can be experienced

for even low head dams if karstic conditions are advanced.

On the basis of median grout takes reported at a number of



Table 1: Precedent Examples of Some Dams Built on Karstic Foundations

Project DamTypeandDate Head(m) GeologyNo.of

GroutLinesSeepage

Remedial

Work

J. Percy

Priest Dam

Earthfll/Concrete

1963-6835.4

Thin-bedded limestone, solu-

tioned jts, sinkholes2 - 4 N. R. N. R.

Sainte Croix

Dam FranceArch 1971-74 72 Cavernous limestone 1 Negligible N. R.

Quinson Dam

FranceArch 1971-74 45 Cavernous limestone 1 Negligible N. R.

Grand Rapids

G. S. Canada

Earthfll/Concrete

1962-6436.5

Dolomite limestone, sinkholes,

solution channels1 Minimal None

Arnprior G. S.

Canada

Earth/Rockfll/

Concrete gravity

1972-76

21Limestone, Solutioned jts, voids

1 cm - 1 m wide3 - 4 l/s N. R.

Lar Dam IranEarthfll

1972-8198

Limestone, advanced karst,

caverns, voids1

Extreme

9 m3/s

Yes

(see text)

Stewartville

Dam Canada

Concrete

gravity/EarthfllCompleted 1948

41

Crystalline limestone open

seams at depth 1 370 l/s Yes.3

Francisco Zarco

Dam Mexico

Earthfll/Concrete

Completed 196823

Limestone, solution channels,

mode karst3 1000 l/s None

La Amistad

Mexico/U.S.A.

Rockfll/Concrete

Completed 196830 Limestone, caverns, sinkholes 1 Minimal None

Sklope Dam

YugoslaviaRockfll 80

Limestone, advanced karst,

caverns1 - 2 500 l/s None

Globocica Dam

Yugoslavia

Rockfll

Completed 196580

Limestone, med. to adv. karst,

solution channels3 4 l/s Yes.4

Hales Bar Dam

U.S.A.

Earthfll/Concrete

1905-19135 11.5

Limestone, solution jts., cavi-

ties, caverns 1

Max. 48

m3/s Yes.

6

Great Falls

U.S.A.

Concrete gravity

Completed 191645.7

Limestone, solution channels,

cavities1 12 m3/s Yes.7

Normandy Dam

U.S.A.

Concrete gravity/

Earthfll 1972-7617

Limestone with shale, clay solu-

tion cavities1 - 2 Negligible None

Pueblo Viejo

Dam GuatemalaRockfll 1977-83 92

Limeston & dolomite, advanced

artesian karst1 - 2 25 l/s None

Punt Dal Gall

Switzerland

Arch

Completed 1969100

Dolomite limestone, calcareous

sandstone, deep karst, solu-

tioned jts

1 50 l/s None

La Bolera Dam

Spain Arch 1961-68 45 Limestone, advanced caverns 1 600 l/s None

Sprinagarind

Dam Thailand

Rockfll/Concrete

1974-80113

Calcareous sandstone, lime-

stone, solution cavities3 25 l/s N. R.

King Talal Dam

Jordan

Rockfll/Concrete

gravity Completed

1971-75

100Karstic limestone to 30 m below

calcareous sandstone1 63 l/s None

La Angostura

Dam Mexico

Rockfll/Concrete

1971-7589

Limestone, clay seams and

solutioned jts2 100 l/s None

3 Asphalt grouting in 1985 reduced leakage by up to 33 l/s

4 Grout curtain extended in left abutment in 19745 Demolished 1960

6 Extensive in 1944

7 Cement and asphalt grouting performed


5/9

Figure 3 Precedent Examples of Grout Curtain Extension into Abutments16

RatioofGroutCurtainExtentioninto

Abutmen

tstoHydraulicHead

00

Maximum Normal Hydraulic Head (m)

Open symbol indicates that remedial work

or excessive seepage (>300 l/s) was reported.

2

4

6

8

10

12

14

20 40 60 80 100 120 140 160 180

Slightly Karstic

(grout take 0 to 50 kh/m)

Highly Karstic

(grout take > 400 kg/m)

Karstic

(grout take 50 to 400 kg/m)

Grout take not reported

Figure 4 Kavar Reservoir and Dam Site

Razak Formation

Asmari Formation

Fault Line

Full Service Level (FSL)Reservoir Rim

Existing River

DamLocation

Lower Reservoir

Upper Reservoir

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precedent dams reported in the literature, triple line grout-

ing can be seen to reduce post impoundment risks (Figure 2)

It is also clear from Table 1 that a signicant factor

governing the performance of grout curtains in karst foun-

dations is whether or not the curtain is anchored into an

impervious base. For example, at the 11.5m high Hales Bar

dam, post construction seepage reached 48 m3 per second

through the hanging curtain. Similarly, at the FranciscoZaro Dam, seepage ows in the order of 1000 L/sec through

the hanging curtain were measured, despite the fact that a

triple line grout curtain had been used.

It is usually necessary to extend the grout curtain some

distance along the dam axis into the abutments to reduce

risks associated with end run seepage. The amount of exten-

sion required can be somewhat subjective, and is dependent

on geological conditions such as the existence of an impervi-

ous boundary. However, for dams founded on a moderately

permeable karstic foundation, a review of precedent would

suggest that the amount of extension required to minimizerisk varies logarithmically as a function of the hydraulic

head (Figure 3).

Asphalt Grouting

When remedial grouting is required after impounding, the

TVA and others have reported good results using hot asphalt

grouting. In this technique, asphalt is melted and pumped

through heated pipes into open cavities. On contact with

the water, the asphalt cools and assumes a globular form

that progressively blocks the solution channels. On various

projects, the TVA has adopted a wait and see approach to

the issue of reservoir watertightness using asphalt grouting

for spot treatment after impoundment often followed by a

program of cement grouting to ensure the long term stabil-

ity of the seal.

TheKavarReservoirThe Kavar site is situated in a mountainous region about 70

km south of Shiraz, Iran, in the Kavar valley. To provideirrigation water, a 60m high concrete faced rockll dam is

planned to impound the Qareh Aghaj River.

Site Conditions

As indicated on Figure 4, the project site can be character-

ized by two distinct regions, a broad upper reservoir and

a lower reservoir. The lower reservoir is contained within

a relatively steep sided canyon where the dam is located.

The elevated margins in the upper reservoir and the steeply

dipping right abutment of the lower reservoir at the dam

site are composed of a strong, moderately to highly karsticlimestone known as the Asmari formation. Weaker Razak

marls are present, locally, within the base of both the upper

and lower reservoirs and form the relatively shal low dipping

left bank of the lower reservoir.

Bedrock Geology

The Asmari Limestone is highly permeable to great depths

throughout the site area due to the existence of solutioned

channels that formed along and across bedding planes.

This has created an unpredictable system of interconnected

ow channels and a rock mass permeability in the order of100 Lugeons and higher. The characteristics of the Razak

formation vary across the site. At the dam site, the Razak

formation is highly deformed as a result of the intense fold-

ing that was responsible for the creation of the canyon itself.

The geologic environment has produced gypsum formations

along bedding planes as well increased hydraulic conductivi-

ties in the range of 10 to 50 Lugeons. In the upper reservoir,

the Razak is generally undeformed and was found to be es-

sentially impervious.

Overburden Conditions

In the upper reservoir, overburden consists of a broad, deep

deposit of lacustrine materials anked on the margins by

slopewash. Both the slopewash and lacustrine materials

were found to be of relatively low permeabi lity. In the

immediate area of the river channel, coarse grained, per-

vious, river alluvium is present. However, it is completely

surrounded by the relatively impervious slopewash or lacus-

trine materials. This distribution of overburden materials

forms a natural impervious blanket, eectively isolating the

pervious Asmari limestone formation from the future res-

ervoir. At the dam site, there are no lacustrine deposits and


6/9

Figure 6 Seepage Control Measures at the Kavar Dam

Concrete Facing

EL. 1665 m (Reservoir Level)

EL. 1626 m

GypsumSurcharge Plastic Concrete Cutoff Wall

Conceptual Location of Gypsum BedGrout Curtain

EL. 1605 m

EL. 1535 m

11

EL. 1640 m

Rock Fill

EL. 1671 m

EL. 1595 m(Assumed Downstream Groundwater Level)

4A5

Impervious Fill

Semi-Pervious Fi llUpstreamCofferdam

DownstreamCofferdam

Figure 5 Conceptual Sketch of Selected

Lower Reservoir Water Tightness Scheme

Reinforced ShotcreteMembrane 10-8

Impervious Blanket toMaximum Reservoir Level 10-5

1660 m(Maximum Reservoir El.)

Slope Wash 10-3

AS 10-2

30-80 m

Undeformed Razak 10-5

Deformed Razak10-3 to 10-4

6 www.powergenu.com

the river alluvium can come in contact with, or be very close

to, highly pervious bedrock. In addition, slopewash materi-

als were found to be signicantly more permeable than in

the upper reservoir area due to the fact that these materials

originated as a result of the mass movement of considerably

steeper rock slopes, thereby producing a coarser material.

Groundwater ConditionsIn the lower reservoir val ley, groundwater levels were found

to be about 10m below the river level, conrming the pervi-

ous nature of the bedrock and the need to seal the reservoir.

ReservoirTreatment

On the basis of the explorations undertaken at the site, a

clear picture of the nature of the foundation conditions, and

the problems that they presented, was developed. In the

upper reservoir area most of the leakage would be forced,

under a moderate head, through the impervious lacustrine

materials and/or the low permeability slopewash that blan-ket the bedrock side slopes before reaching the pervious

Asmari bedrock. Therefore, provided that local treatment

of exposed Asmari outcrops in the upper reservoir was un-

dertaken, losses would generally be minimal. On the other

hand, in the lower reservoir area, leakage will occur under

relatively high head through relatively pervious slopewash

into the immediately adjacent pervious Razak bedrock and/

or directly into the right abutment highly pervious Asmari

formation. Limiting seepage losses to manageable levels in

this area, therefore, required a comprehensive treatment

plan to seal the entire ooded canyon.

Originally, it had been planned to use of a complex

grouting scheme to tie the highly pervious Asmari into,

what was assumed to be, impervious Razak bedrock us-

ing a technique similar to one that had been successfully

employed at the El Cajun project. However, as the explo-

ration program evolved, it became apparent that both the

upper portion of the Razak, and the overlying slopewash

materials, were signicantly more permeable than had

been previously assumed. To reduce concerns regardingsubsurface unknowns, and the reliance on grouting to great

depths to adequately seal the foundation, an alternative wa-

tertightness treatment using a surcial impervious surface

membrane was developed as shown conceptually in Figure

5. On the relatively steep right bank where the Asmari out-

crops, the membrane consists of a 120 mm thick, silica fume

reinforced shotcrete membrane anchored into the slope. In

the valley bottom, and over the left bank where relatively

at slopes exist due to the presence of the Razak formation,

an overburden blanket, consisting of compacted impervi-

ous and erosion protection lls is planned. This treatment

wil l cover the entire lower reservoir area, extending ap-

proximately 700-800 m upstream of the dam site to the

upper reservoir where it will be connected into the natural

impervious materials that exist there. Although unusual, as

shown on Table 2, the use of shotcrete for sealing a dam or

reservoir is not unprecedented.


7/9

Figure 7 The Effect of Gypsum Particle Size

on the Contact Time Required for Saturation1.0

0.4

0.2

Concentration

Ratio

0

0

Contact Time (Days)

0.5mm Particle Size

0.1mm Particle Size Saturation

50 150 250100 200 300

0.6

0.8

Figure 8 Estimated Mass Removal Rates

for the Gypsum Surcharge at the Kavar Dam

800

320

80Masso

fGypsum

Remove

dper

Un

it

Surc

harge

Area

(kg

/sq.

m)

0

0

Time After Reservoir Impoundment (Years)

Upper Bound

70 kg/sq.m/year

Lower Bound2 kg/sq.m/year

1 2 3 4 5 6 7 8 9 10

160

480

640

400

240

560

720

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To further reduce the likelihood of any future problemsassociated with progressive dissolution of the gypsum

beds known to exist above a depth of 50 m in the Razak

formation at the dam site, a plastic concrete cut-o wall is

planned. This will be supplemented by a double line grout

curtain to reduce seepage gradients across the cuto, and

to further reduce the bedrock permeability. Details of the

treatment measures planned at the dam site are shown on

Figure 6.

TheGypsumSurcharge

Another unique feature of the treatment measures used at

the Kavar site is a gypsum surcharge that is to be installed

immediately upstream of the dam. The purpose of the

surcharge ll is to cause water seeping through the ll to

become saturated with dissolved gypsum at a concentration

as close as possible to the solubility limit, similar to a con-

cept reported by Pokrovskii, 1994 in which salt solutions are

injected into the foundation of dams constructed on rocks

containing water-soluble salts (ha lite).

To assess the gypsum requirements for the dam, the

approach of James and Lupton for particulate forms of gyp-

sum and anhydrite was used. Key parameters in the analysis

included the density, D, of gypsum 2300 kg/m3, the initiallinear particle size lo, the particle volume coecient b (vol.

=bl3), the particle area coecient a (area= al2), the solubil-

ity rate constant K, and the solubility limit cs of gypsum.

As a rst step, ow nets were constructed to estimate the

hydraulic ux through the gypsum surcharge. The thick-

ness of the gypsum bed could then be designed by assuming

advective transport only (i.e., neglecting diusion). In this

way, the dissolved mass of gypsum leaving the surcharge

per unit area could be approximated by the product of the

gypsum concentration and seepage ux per unit area of

surcharge. The calculated ow rate through the gypsum

surcharge was found to vary from 2.0x10-6 to 9.5x10-5cm/

sec. Based on an assumed porosity of 0.3, seepage velocities

through the gypsum bed were estimated to vary between

6.7x106cm/sec and 3x10-4 cm/sec.

The size of surcharge required is based on the design

life of the project and the amount of time required to en-

sure that the seepage water owing through the gypsum

surcharge area is fully saturated with gypsum. To achieve

the required contact time with a reasonable sized surcharge

ll, a number of alternatives were considered, including:

increasing the surcharge thickness, reducing the hydraulic

Table 2: Summary of Examples of Shotcrete used as for Water Tightness Treatment

Project Country Date Structure DescriptionLength

(m)

Height

(m)

La Joie Canada 1955Timer aced

rockfll damGunite used to seal deteriorated timber aced dam 400 60.0

Leichhardt

RiverAustralia 1957 Rockfll dam

Reinorced gunite used as sole impervious ele-

ment or rockfll dam260 26.5

Corella Australia 1957 Rockfll damReinorced gunite used as the sole impervious

element146 23

Hammam

GrouzAustria 1987

Concrete

gravity dam

Shotcrete and clay blanket used to seal karstic

limestone reservoir slopes50 36.0

Tranavka Czech 1988 Earth dam Shotcrete and plastic membrame used or sealing 20.0

Jordan

RiverCanada 1989

Amberson

buttres damShotcrete used or sealing 29.0

Eastside

ReservoirUSA 1998

Blasted rock

SlopesShotcrete used or sealing the reservoir 250 50.0



conductivity of the impervious blanket within 100 meters

of the upstream plinth and reducing the particle size of

the gypsum. The most eective means of enhancing con-

tact time was found to be reducing the particle size. For

example, as shown on Figure 7, as gypsum particle size is

reduced from 0.5 mm to 0.1 mm, minimum contact times

reduced from 200 to 40 days.

On this basis, the Kavar surcharge was designed as a 5m thick mixture of 40% (by weight) ground gypsum, with

a maximum particle size in the range of 0.1 to 0.5 mm,

thoroughly mixed with ne a grained soil. This produces

an engineered ll with a dry unit mass of 1900 kg/m3 and

a permeability in the desired range of 10-4 to 10-5 cm/sec.

As indicated in Figure 8, for this design, the annual mass

removal rate is expected to vary between 2 kg to 70 kg per

square meter of surcharge. For the 3,800 kg Kavar sur-

charge, this will result in a service life of at least 50 years.

ConclusionsTechniques exist to treat even highly karstic foundations.

However, for treatment measures to be eective, a thorough

understanding of the site conditions is essential. At the Ka-

var Dam, an unusual combination of a surface membrane,

in combination with a gypsum surcharge and other seepage

control measures, is planned to deal with the complex foun-

dation problems that had been identied.

References

Fischer, J.A. and Fischer, J.J., 1995. Karst site remediation grouting.

Karst GeoHazards: Proc. 5th Multidisciplinary Conference onSinkholes and the Engineering and Environmental Impacts ofKarst.Balkema, Roterdam, pp. 363-369.

Freeze, R.A. and Cherry, J.A. , 1979. Groundwater, Prentice HallInc., Upper Saddle River, New Jersey., pp. 383-462.

James, A.N. and Kirkpatrick, I.M., 1988. Design of foundations ofdams containing soluble rocks and soils. Quarterly Journal ofEngineering Geology, Vol. 13, pp. 189-198.

James A.N., and Lupton, A.R. 1978, Gypsum and anhydrite infoundations of hydraulic structures. Geotechnique, Vol. 28,No. 3, pp. 249-272.

Pokrovski i, G.I., 1994. Combined methods of protecting saliferousfoundation soils of hydraulic structures from dissolution.Hydrotechnical Construction Vol. 28, No. 10, pp 10-14.

Soderberg, A.D., 1988. Foundation treatment of karstic featuresunder TVA dams. Geotechnical Aspects of Karst Terrain,

ASTM Geotechnical Special Publication No. 14, pp. 149-165.

Uromeihy, A. 2000. The Lar Dam; an example of infrastructuredevelopment in a geologically active karstic region. Journalof Asian Earth Sciences, Elsevier Science , vol. 18, no. 1, pp.25-31(7).

Welsh, J.P., 1988. Sinkhole rectication by compaction grouting.Geotechnical Aspects of Karst Terrain, ASTM GeotechnicalSpecial Publication No. 14, pp. 115-132.

Zuomei, Z. and Pinshou, H., 1988. Grouting of the karstic caves

with clay llings. Geotechnical Aspects of Karst Terrain,ASTM Geotechnical Special Publication No. 14, pp. 92-104.

Fookes, P. G., and Hawkings, A. B., 1988. Limestone weathering:its engineering signicance and a proposed classicationsystem. Quarterly Journal of Engineering Geology, London,Vol. 21, pp. 7-31.

ACKNOWLEDGEMENTS:This course is based on the presentation entitled The Design

of Foundation Treatment Measures for Dams on KarstFoundations as presented at Waterpower 2001. The authorsfor this paper are acknowledged as C. R. Donnelly and S.Hinchberger of Acres International, and E. Mohammadian ofDezab Consulting Engineers. Portions of the original paperhave been modied for this course.


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1. Karsticity occurs as a resultof a progressive disolutioningof carbonate rocks exposed to

water and carbon dioxide.

a. Trueb . Falsec. I dont know what Karsticity is

2. In the presence of dissolved carbondioxide, maximum concentrationsincrease dramatically, account-ing for the fact that seepageowing from karst formations

often contains up to _____mg/L of calcium carbonate.

a. 200b. 300c. 400d. 600e. 800

3. A karstic formation impliesthe presence of a network ofsolutioned, often highly permeable,discontinuities which are, bydenition, connected to the surfaceso that the free carbon dioxidenecessary to allow the solutioningprocess to continue is available.

a. Trueb. False

4. The diculties involved inconstructing a dam on a karsticfoundation were rst documentedat ____ ____ dam that was built byprivate interests on the Tennessee

River between 1905 and 1913.a. Hails Boxb. Hills Barnc. Hales Bard. Hanes Bar & Grill

5. The problems at dams that havesevere seepage or leakage arelikely related, at least in part, toan inadequate understanding ofthe _____ of karst prior to thecommencement of construction.

a. depthb. typec. colord. strength

e. All of the above

6. Successful treatment of karstic

foundations requiresa. a means of reducing the

amount of seepage

b. techniques to prevent dissolution

of soluble minerals that may be

present in the foundation

c. methods to ensure that the

foundation has adequate capacity

to resist the post impoundment

loadings without excessive settlement

d. All of the above

7. Foundation treatment for karstic

formations typically includes

consolidation grouting to

a. increase adequate bearing strength

b. minimize settlements

c. reduce subsurface water ows

d. seal void areas

8. Compaction grouting typically

results in hydraulic fracturing,

extrusion and consolidation

of clayey llings within the

sinkholes increasing strength, and

resistance to seepage stresses.

a. True

b. False

9. The most commonly occurring

soluble rock mineral(s) are

a. calcium carbonate (limestone)b. gypsum

c. anhydrite

d. halite

e. All of the above

10. Mitigation of the risk of solutioning

in a foundation containing such

minerals as calcium carbonate,

gypsum, anhydrite, and halite

requires reducing the volume of

a. karstic voids

b. subsurface groundwater

c. seepage and seepage gradients

d. hydraulic gradient

11. An active brine injection system

has been used to treat foundationscontaining halite mineral deposits.

a. True

b. False

12. The Median Post Impound-

ment Seepage of approximately

50 l/sec would require

a. 1 line of grout

b. 2 lines of grout

c. 3 lines of grout

d. 4 lines of grout

13. It is usually necessary to extend

the grout curtain along the dam

axis into the abutments to

reduce risks associated with

end run seepage. The amount

of extension is dependent

a. on geological conditions

b. on economic impacts

c. on diculty of install ing

the grout curtain

d. on the schedule of remediation

14. Hot asphalt grouting is a technique

where asphalt is melted and

pumped through heated pipes into

open cavities. On contact with the

water, the asphalt cools and as-

sumes a globular form that progres-

sively blocks the solution channels.

a. True

b. False

15. At the Kavar Project, the proposed

reservoir treatment included an

impervious surface membrane; an

overburden blanket, consisting

of compacted impervious and

erosion protection ll; a reinforced

concrete shotcrete membrane;and a gypsum surcharge.

a. True

b. False

foundation tratment

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