01 Önemli Cave

Engineering Geology 51 (1999) 167–182

The geological problems of the large dams constructedon the Euphrates River (Turkey)

Aziz ErtuncCukurova University, Department of Geological Engineering, Adana, Turkey

Abstract

In order to use the energy and irrigation potential of the Euphrates River, a series of dams have been designed(upstream to downstream); Keban, Karakaya, Karababa (Ataturk), Birecik and Karkamis. The first three of thesedams have been completed; construction on the Birecik and Karkamis dams is underway. The initial plans involveda 60 m high Golkoy dam, downstream of the Karakaya dam, with the Ataturk dam 60 m lower than it is currently.In the belief that the cost of irrigation by the Ataturk dam’s water would be high, the increase of the height ofAtaturk dam was preferred to the construction of the Golkoy dam. The Keban dam’s basement is formed by karsticrock, named Keban marble. From the author and his colleagues’ studies, it has been shown that water would leakfrom the left side of Keban dam reservoir, forming a spring in the Keban Creek. In order to prevent this waterleakage, an intensive grouting programme was applied. In spite of this, when the reservoir was filled, 26–30 m3/s ofwater leaked from the Keban Creek. A more recent study on the volume of leakage showed it to be reduced to7–8 m3/s, with this amount remaining constant. The Karakaya dam is constructed on metamorphic rocks thus onlyallowing minimal water leakage. However, on the downstream side of the right slope, the Tillo–Bego–Senketolandslides have been an important risk to the dam. If such landslides cause an artifical lake by blocking the EuphratesRiver, the Karakaya hydroelectric power station could be flooded. Limestone forms the foundations for the Ataturkdam. On and around the damsite, there is epithermal water (24–26°C) below the aquifer, deeper than 300 m, withthe level of the grouting curtain down to 180–200 m. The grouting curtain would not be able to prevent the leakagebecause the level of karstification extends below the grouting curtain. In February 1993, the total volume of leakingwater from the damsite and its vicinity reached 10 m3/s when the reservoir level was 517 m. When the reservoir is full(542 m), the volume of leaking water is expected to increase. Under the clay core of the dam, extending from thesurface to 30–40 m depth, high grouting pressure could not be applied, so water leaked at this part of the groutingcurtain and thus the amount of leaked water could not be measured. © 1999 Elsevier Science B.V. All rights reserved.

Keywords: Dam; Landslide; Grouting; Watertightness; Karstification

1. Introduction Tigris, where it flows into the Persian Gulf. Itsregulated average discharge in Keban is 650 m3/sand in Karkamis (Syria boundary) it is 963 m3/s.The Euphrates River is the most important riverIn order to exploit the energy and irrigationalin south-eastern Turkey; it is formed from thepotential of the Euphrates River, a series of damsKarasu and Murat tributary rivers. This river,have been designed (upstream to downstream) atwhich is 2800 km in length, crosses East Anatolia,

enters Syria and then crosses Iraq to join the Keban, Karakaya, Karababa (Ataturk), Birecik

0013-7952/99/$ – see front matter © 1999 Elsevier Science B.V. All rights reserved.PII: S0013-7952 ( 97 ) 00072-0

168 A. Ertunc / Engineering Geology 51 (1999) 167–182

Height from foundation 207 mand Karkamis. The first three of these dams haveHeight from river bed 163 mbeen completed, with construction on the BirecikMaximum water surface 846.67 mand Karkamis dams underway. The initial plans

elevationhad a 60 m high Golkoy dam, downstream of theNormal water surface 845 mKarakaya dam, with the Ataturk dam 60 m lower

elevationthan it is currently. In the belief that the pumpingReservoir volume at normal 30 600 km3expense of irrigation by the Ataturk dam’s water,

surface elevationthe increase in the height of Ataturk dam wasReservoir area at normal 675 km2preferred to the construction of the Golkoy dam

surface elevation(Figs. 1 and 2).Number of units 4+4Unit capacity (157.50+175) MW1.1. General characteristics of the Keban damInstalled capacity 1330 MWAnnual energy generation 6000 GWhType rockfill+concrete

gravityPurpose energy 1.2. General characteristics of Karakaya damDam volume 15 585 000 m3Crest elevation 848 m Type concrete gravity

and archCrest length 1097 m

Fig. 1. Positions of dams on the Euphrates River.

169A. Ertunc / Engineering Geology 51 (1999) 167–182

Purpose energy Mean annual flow 963 m3/sTotal volume of fill 10 million m3Dam volume 2 000 000 m3

Crest elevation 698 m Total volume of 1.5 million m3concreteCrest length 462 m

Height from foundation 173 m Number of units 6Installed capacity 672 MWHeight from river bed 156 m

Maximum water surface 693 m Annual energy 2500 GWhgenerationelevation

Minimum water surface 670 melevation 1.5. General characteristics of Karkamis dam

Number of units 6Installed capacity 1800 MW Type clay coredAnnual energy generation 7500 GWh sand–gravel fill

Purpose energyHeight from foundation 29 m1.3. General characteristics of Ataturk dam:Height from river bed 21.20 m

Type rockfill Dam volume 2.1 hm3Purpose irrigation Crest length 1647 m

and energy Normal reservoir elevation 340 mDam volume 84.5×106 m3 Reservoir area 28.4 km2Crest elevation 549 m Reservoir volume 156.9 hm3Crest length 1914 m Number of units 6Height from foundation 176 m Installed capacity 189 MWHeight from river bed 169 m Annual energy generation 652.5 GWhMaximum water surface 542 m

elevationReservoir volume at normal water 48.5 km3 2. Keban dam

surface elevationReservoir area at normal water 817 km2 The Keban dam was the first of the large dams

surface elevation to be built on the Euphrates River (Fig. 3). TheNumber of units 8 purpose of the dam is for hydroelectric power.Installed capacity 2400 MW

The right side of the dam is rockfill, with the leftAnnual energy generation 8900 GWh

side being concrete gravity.

1.4. General characteristics of Birecik dam2.1. Geology

Type concrete gravity+clayThe Nimri formation forms the oldest unit ofcored sand–gravel fill

the Paleozoic metamorphic basement in the studyPurpose energyarea (Fig. 4). This formation, with limestone gen-Height from the 62.5 merally dominant, consists of medium to thickfoundationbedded limestone and dolomite (grey, black andHeight from the 49.5 mbeige in colour, massive and hard in texture),river bedalternating with yellow, beige, brown, green andCrest elevation 389.5 mred schist. As a result of the lateral and verticalCrest length 2510 mfacies changes, it is generally observed that theReservoir area 56 km2limestone, and in places the schist, is dominant.Reservoir volume 1.2 km3On the Nimri formation, there is Keban marble.Normal reservoir 385 m

elevation The Keban marble is white, pinkish, light and


Fig. 2. Euphrates River projects.

dark grey coloured, hard and competent, with transgressively over the Keban marble. This con-glomerate is composed of dark grey to blackbedding generally unnoticeable. It is laminated,

fissured and faulted at various places with closely recrystallized limestone and marble with a fewquartz and quartzite fragments within the matrixspaced jointing. The 200–500 m thick Keban

marble has been subject to intensive karstification, that consists of calc–schist and micaceous schist.The conglomerate is very hard, competent andforming many cavities. A basal conglomerate lies


Fig. 3. Keban dam, view from right side to left side.

medium to thick-bedded, with a thickness variation older units in the south above the reservoir levelin the study area. It consists of an alternation ofbetween 10–150 m. The upper schist, named the

Delimehmet formation, covers the irregular paleo- sandstone, marl, conglomerate and dominant lime-stone. The limestone is beige coloured, thin–topography of the Keban marble. It consists of

chlorite-bearing micaceous schists. Marble lenses medium bedded, hard, closely jointed and containsabundant Nummulite fossils. The sandstone is red,are seen in the lower levels and are intercalated

with conglomerate. The thickness of the formation light brown–beige coloured, thin to mediumbedded, is limy cemented and richly fossiliferous.is estimated to be over 1500 m.

In the study area, a flysh named the Sagdiclar The marl is grey coloured, thin bedded and incom-petent, causing vast landslides. The conglomerateformation produces an outcrop above the reservoir

level (elevation 845 m); therefore, it only has strati- contains black limestone, white marble and beigecoloured schist elements of gravel–boulder sizesgraphical importance. The flysh consists of an

alternation of red limestone containing radiolaria, and is limy cemented. Their total thickness maychange from several metres up to 200 m. The agegreen sandstone of magmatic origin, conglomerate,

beige limestone and mudstone. The thickness is of this formation is Eocene–Oligocene. Magmaticrocks cover large areas in the east of the studyestimated to be 100 m around the village of

Sagdiclar dating to the Campanian–Maastrichtian. area and in the vicinity of Keban town. Theyconsist of rock such as syenite, diorite, diabase,The Kuscu conglomerate, dating to the

Paleocene–Eocene, covers a large area above the basalt and spilite. In the vicinity of the dam axis,major faults have developed at the contact betweenreservoir level. The conglomerate is limy, cemented

and contains black–grey, white limestone, yellow- competent marble and the upper schist, and withinthe marble mass. The fractures in the marbleish schist and magmatic gravels. Its maximum

thickness is estimated to be 300 m. follow partly the drainage pattern (Ertunc andHadimli, 1971).The Seko formation forms the cover over the


Fig. 4. Possible leakage courses from left reservoir rim of Keban dam.

2.2. Engineering geology excavations, large caves were exposed and laterfilled with concrete; inaccessible caves were filledwith intensive grouting.The problems that arose from the construction

of Keban dam were investigated in the literature During the dam’s construction, a 1:25 000 scalegeological map was made of the area bounded byand helped in the understanding of the importance

of engineering geology in Turkey. The dam’s base- the Murat branch of the Euphrates River in thenorth, by the Geyiktasi Hill location (25 km down-ment is karstic rock, named Keban marble. It is

jointed, fissured, faulted and has many cavities stream from the dam site) in the south, by themarble mass covering a large area in the east, andthat can be seen from the surface. The data

obtained by borings and tunnel investigations were by the Euphrates River in the west (Fig. 4). Thisgeological study was carried out by the author andinsufficient. On boring at the site of the power

station, a large cave was seen, as demonstrated on his colleagues. As a result of this study, the possi-bility of the water leakage from the left side of thethe borehole log. However, in spite of this, the

power station was located there. During the base- reservoir was envisaged. The Keban marble whichoutcrops like a lens along the reservoir extendsment excavations, the cave was observed and

caused the power station to be relocated down- from the left bank to Keban Creek, Pamuk Creekand Zeryan Creek in the south. The reservoir’sstream. When a cavity was discovered on the

basement of the concrete gravity, it was turned by maximum elevation is 845 m. The marble outcropof Keban Creek is 750 m; at Pamuk Creek it is90° and then making it parallel to the dam to

avoid the cavity, and the concrete gravity was 800 m and it descends to 770 m at Zeryan Creek.In the boreholes of the Keban marble, the watershifted downstream (Fig. 3). During the basement

Berk

Vurgu

Berk

Yapışkan Not

Önemli cave felan


level was found to be lower than the Euphrates calcitic drip stone occurred. The karstic phen-omena is very much developed at the damsite.River and Keban Creek. During fieldwork, a lot

of cavities on the surface were found. After this Downstream of the dam, on the left bank of theEuphrates River, a spring exists. Its capacity wasstudy, it was seen that if a grouting curtain from

the left bank to the east, reaching the schist, was estimated to be about 0.5 m3/s. In the Kebanmarble on the valley abutments, karstification isnot built, leaking water would spring from Keban

Creek, and some would reach and spring from very well developed on the main faults. From thesefaults, smaller karstic channels branch; these arePamuk and Zeryan Creeks (Ertunc et al., 1972).

In the region of the Keban marble immediately developed tectonic joints and fractures. This isvisible, for example, in the Keban marble inbelow the transgressive contact with the upper

schist, karstic cavities were found in roadcuttings Kameroglu Creek valley. Exploration holes in thisregion found (at great depth in the marble nearnear Keban Creek, on the walls of the deep cut of

the intake approach channel, as well as near the the Figen fault) karstic channels with sedimentsindicating hydrothermal origin (borehole K-3).left gravity wing. The cavities were filled with

thinly bedded sediments, which were diagenetically This confirms the above-explained pattern ofdevelopment of these karstic phenomena. On thepetrified and later folded and fissured. In a later

phase, a basic net of deep karstic channels was above-mentioned recently exposed surface of theKeban marble in the Keban Creek, there are onlydeveloped, generally from the bottom upwards.

This involved the above-mentioned older cavities traces of superficially developed shallow karsticdissolution (Bozovic et al., 1972).having thinly bedded sediments in which new

channels were opened. In this new net of karstic The grouting had started from a platform con-structed on the left bank of the dam (Fig. 5). Thechannels, there are a variety of calcitic and other

deposits, which indicate hydrothermal activity. The platform’s elevation was about 850 m. Originally,the grouting depth was planned to be 250 m, butassumed hydrothermal development of the karstic

channels is supported by the fact that travertine as the karstification reached deeper on some sides,grouting was extended to 300–350 m depth. Thisdeposits exist on the left bank of the dam site, on

top of the karstic channels. In the Keban marble grouting curtain was connected to the dam sitegrouting curtain ( Kosar, 1981).region, there are a few dykes of syenite–porphyrite.

The greatest outcrop of such igneous rock is near After the reservoir was filled with water, to amaximum level of 845 m, shown by point S.H. onKeban town, in which fissured traces of hydrother-

mal sediments are found, as well as traces of Fig. 5, the leakage water from the sink hole disap-peared by making a whirlpool. Below the rivermalachite and azurite. In the boreholes K-5, K-2

and LP-10, deep in the Keban marble, the same bed (175 m), the Crab Cavity, with a volume of110 000 m3, was discovered. By following the leak-syenite rock was found, and east of the zone of

these holes, a continuous outcrop of igneous rock ing water, the Petek Cavity with a volume of600 000 m3 was discovered.is found. These results indicate hydrothermal activ-

ity. The net of karstic channels developed by this At the same time, at Keban Creek, the leakingwater capacity, increasing with an elevation levelhydrothermal activity has smooth walls, and does

not greatly involve the adjacent joints and fissures; of 750 m as mentioned above, was seen to bespringing with a capacity of 26–30 m3/s (Fig. 4).the only exceptions to this are the heavily fractured

fault zones. In the declining phase of the hydro- The water sprung from the left side of KebanCreek by making a syphon. The reservoir levelthermal activity, calcite deposits were formed,

which obstructed and closed the channels. In addi- was immediately lowered to the sink hole wherethe leakage started, the sink hole was surroundedtion, some sedimentary deposits were found inter-

woven with calcite veins. When water stopped by a concrete wall, and Petek Cavity was filledwith rock blocks. Filling was time consuming, butrising through the net of channels, surface water

temporarily flowed and deposited loose beds of the water leakage capacity from Keban Creekdecreased to 7–8 m3/s, remaining constant (Figs. 6clay and sand. In this phase, some formation of


Fig. 5. Grouting curtains location map.

Fig. 6. Leaking water from left side of the Keban Creek.

and 7). At Pamuk and Zeryan Creeks, the sub- part of the electrical energy of Turkey is nowsupplied from the Keban dam.surface water level was raised forming a small

spring. As the average discharge of the EuphratesRiver water is 650 m3/s, this 7–8 m3/s water leak-age from the creek is minimal. Even in the seasonswhen the capacity is full, some of the water from 3. Karakaya damthe spillway is released. Because of these arisingproblems, the Keban dam’s completion was Karakaya, a concrete gravity and arch dam, is

constructed on the Karakaya metamorphic rocksdelayed and its cost rose. However, an important


Fig. 7. Leaking water at the left side of Keban Creek forming a syphon.

(Fig. 8). The purpose of the dam is for hydro- present, it is hard to decide a type locality and theprogress of metamorphism. The best, and seem-electric power.ingly most complete exposure, lies betweenHindibaba and Karakaya villages. Over the per-3.1. Geologyformed structure sections, the thickness shouldreach approximately 2000 m. Based upon the min-The oldest outcrops are made up of various

metamorphic schists of possible Paleozoic age. The eral composition and the texture of the metamor-phic rocks, this sequence can be divided into threeKocali complex of the Upper Jurassic–Cretaceous

is allochthonous. Over the northern portion of the subdivisions, namely: (1) metapelites (metagrey-wacke, slate, phyllite and intermediate type, schist,study area, the oldest sequence of Cenozoic age is

the Gercus formation (Lower Eocene). It is over- gneiss); (2) metabasites (basic igneous rocksaffected variously by the metamorphism); and (3)lain by the Midyat and Lice formations, with later

thrusting of the Karakaya metamorphic rocks over carbonates.The Kocali complex is exposed along the deeplythe Lice formation.

The Karakaya metamorphic rock associations incised canyons of the Euphrates River andbeneath the white Midyat limestone and reddisplay an intricate structural evolution. The

Alpine orogeny caused both systematic and non- Gercus conglomerate. There are several irregularKocali complex exposures beneath the Midyatsystematic fractures, and these were added to the

multiple small-scale crenulations and folds. The limestone at Tillo, Bego and Senketo landslidesarea. There are many constrasting rock types inprimary structures are lost by the effects of

repeated later orogenies. Presumably, the repeated this formation, such as limestone, radiolarianchert, basic volcanics, serpentine and marble. Theirmetamorphic episodes are now hard to decipher.

The present outcrops are weathered on flat land, initial position and relationship are lost forever.The radiolarian chert is in the majority along thewith the fresh rock characteristics also being

affected by young hydrothermal alteration. At outcrop between the Hoya and Haburman villages.


Fig. 8. Karakaya dam, view from downstream.

It displays a few irregular limestone and dolostone unconformably the Kocali complex and is con-formably overlain by Midyat formation which isbodies. The thickness amounts to 3500 m and is

overlain by basic volcanics (basalt, agglomerate, a vertical, gradational transition.The Midyat formation outcrops 2 km down-spilite and pillow lava), continuing for approxi-

mately 5 km along the banks of the Euphrates. stream of the Karakaya dam site, extending in thedirection of Gercus county along the EuphratesGercus formation is shown as a strip, cropping

out from beneath the Midyat formation. It is River. It is prominent to the east of Hoya andBagvenk villages, and also at Ayi and Kimil moun-mainly red to pink in colour and its thickness

fluctuates between 10 and 50 m. There also exist tains. At the last locality, the Midyat formation isaffected by huge sliding. The Midyat formationsporadic Gercus formation exposures showing up

from beneath the Midyat formation and over the here is subdivided into three members (bottom totop): a Hoya limestone and dolostone member; aextended landslide country Tillo, Bego and

Senketo territories. There are fine and coarse litho- Mirgan cherty limestone member; and a Cunguslimestone member. The Hoya member is 155 mlogic associations along with the Gercus formation,

but evaporites are not frequently encountered. The thick, the Mirgan member is 220 m thick, and theCungus member is 150 m thick. The Hoya lime-overwhelming red to pink colour is due to ter-

restrial conditions; green, brown, and other hues stone and dolostone member is conspicuous in thefield by its brown weathered topographic surfaces.are subsidiary. The conglomerates are made up of

highly uneven but rounded clasts of limestone, The limestone and the dolostone are interfingering.The former is yellowish, medium–thick bedded,serpentinite and radiolarian chert. In the neigh-

bourhood of Bego village and along Merg Creek, very hard, recrystallized, and superficially affectedby dissolution. The latter is grey–brown and mot-a few gypsum lenses are shown. The detritals are

well consolidated and are prone to mass movement tled, thick bedded, very hard and less affected bysuperficial dissolution. The Mirgan cherty lime-over the slopes. An impure calcite is the most

common cement. The Gercus formation overlies stone member is the middle section of the Midyat


formation. The limestone is light to dark coloured, an area of 45 km2, is the largest in Turkey. Thereexist rock falls, flag slides, rotational blocks andevenly and persistingly thin to thick bedded and

contains whitish-brownish chert nodules parallel sink-lake glide mass. Solifluction is observable atBego village. The Midyat limestone blocks, ofto the bedding. Being softer, it yields into extended

furrows. Superficially, it is affected by dissoluton. various sizes, glide over the wet surfaces of theunderlying Gercus and Kocali wettable lithologies.The Cungus limestone member is a yellow–light

greyish–black colour, medium to thick bedded, Excepting the small-scale slide contact of Midyatwith Gercus, the main body of either Gercus orhard, criss-crossed by white calcite veins, partially

recrystallized and fossiliferous. Kocali is not affected by gliding. Should a naturaldam occur by gliding, the various installations ofThe Lice formation outcrops 500 m downstream

of the Karakaya damsite and extends in an east– the Karakaya dam would be flooded.All the landslides within the study area arewest direction. The maximum thickness may

exceed 1000 m. This formation is made up of marl, caused by the movement of joints and hence arerelated to the rock type, the position of the slope,claystone, sandstone and limestone. Marl is the

most abundant member of the lithologic associa- the influence of weathering, seismicity and theheadward erosional carving of the Euphrates andtion; thus, the others appear as sparse interbeds in

the sequence. All these lithologies are light col- its tributaries. These would reach a greater extentupon a continuous wetting by leakage of the basaloured or, less frequently, yellow–brown and green

in colour and are thin to medium thick bedded; plane and undermining of the slope. The attitudeof the Midyat limestone cropping at Ayi and Kimilthis is a molasse facies. The Lice formation uncon-

formably overlies the Midyat formation and it is mountains, striking NE5–35 and dipping to NW,eases the downdip directed sliding. The joint setstectonically overlain by overthrusted Karakaya

metamorphics. N60E and 90° affecting the Midyat limestone, plusthe others which are not obvious because of Post-Miocene mass movements, are also responsible3.2. Engineering geologyfor sliding.

The Gercus formation is made up of conglomer-The Karakaya concrete gravity and arch dam isconstructed on Karakaya metamorphic rocks; ates with clasts of white limestone, green serpentin-

ite and red radiolarian chert. Gypsum lenses arethere is no problem with water leakage. Some ofthe small landslide effects are unimportant (e.g. subsidiary, such as those present to the south of

Bego and at Merg Creek. The sulphate increasesHaskento landslides). In addition, there has notbeen any significant problems with the dam site, in volume upon hydration, causing upheavals

which would start secondary movements of thebut on the downstream side of the right slope, theTillo–Bego–Senketo landslides have been an overlying Midyat limestone. The meteoric water

seeping along the joint planes and reaching theimportant risk for the dam. If this landslides causean artificial lake by blocking up the Euphrates surface separating the underlying soft and ill-

consolidated Gercus detritals ease the movementRiver, the Karakaya hydroelectric centre wouldbe flooded (Fig. 9) (Erguvanli and Kumbasar, of the formerly detached limestone blocks.

The underlying lithologies of the Kocali com-1967).Extended and harmful down-slope sliding on a plex, which are exposed at Ayi and Kimil moun-

tains, exhibit an old topographic surface dippinglarge scale is restricted to the outcrop expanse ofMidyat formation. Large rock falls are unin- to the north and toward the Euphrates River. The

glidings over the milder dipping stretches are sub-terrupted between Korudag and Hindibaba Creeksand these are triggered by a moving joint set sidiary in comparison with those of the steeper

slope sectors. The degree of observable mass move-running N30W and 90°. The large Midyat lime-stone blocks are detached from the Ayi and Kimil ment is higher during the wetter years. The rain

and melted snow water seeping through the contactmountains and reach Senketo, Bego, Tillo,Merickeni, Savi and Tangol. This landslide, with of Midyat limestone with Gercus at Ayi and Kimil


Fig. 9. Tillo–Bego–Senketo landslides, view from left side to right side (south).

mountains hasten the pace of gliding. The glide prone to further detrimental progress. Eventually,the materials at Sersenden and Cindo Hills anddetritals reaching the Euphrates are carried down

river by powerful currents, but this leaves open the Murho depression would reach Euphrates. Atthe SK-1 borehole, which is situated near thespaces which are hastily filled with downward

moving slope waste. Murho depression, a 113 m thick section of glidematerials was sampled. SK-2 failed to reach theThe landslide area has been geologically and

geophysically surveyed, including mapping to a Gercus and the Kocali formations at 250 m dueto a squeezing of the drill system. At this locality,scale of 1:25 000 and 1:5000. Thus, a three-step

slide strip is differentiated. The lower 8 km long their expected depth was between 250 and 270 m.According to both geological and geophysical com-and 1–1.5 km wide strip extends E–W between the

Tangol, Savi, Merickeni, Bego and the Murho putations, the volume of the slided mass wouldamount to 191×106 m3.depression, exposing a limit to the north with the

Hirso Brook and the Euphrates River. The slides The second step lies to the north of a lineconnecting a point at about 1.5 km to the southbetween Savi, Merickeni and Bego Mill are

directed to Hirso Brook. The Midyat limestone at of Tillo to Ziyaret Hill. It is 7–8 km long and1.5–2 km wide. To the south of that boundary lieBego Mill, Acilar Spring and Ziyaret Hill are in a

continuous glide movement towards the detrital materials of large volume between thesouth of Eyni plateau and the Tillo village. TheEuphrates. This mass is calculated to possess a

volume of 40×106 m3. The surveying was carried detached blocks to the south and south east of theGeyveni hamlet reached the Dolak depression.out by drilling and obtaining undisturbed samples.

The previously glided colossal block at Ziyaret There exists an upheaved stretch of land extendingfrom the east of Dolak depression to the heel ofHill seems to maintain its stable position. There

exists an extended open fissure running from the the landslide. The Dolak depression lodges a land-slide lake; this second step would have moved afterZiyaret Hill to the Murho depression and this is


the first. The lateral compression of the sliding 4. Ataturk dammasses would ease the gliding of the first step.

The Ataturk rock fill dam is constructed onThe third step is 7 km long and 1.5–2 km large.dolomitic limestone, bituminous limestone andIt lies to the south of the second step and is limitedplaquette limestone dating to the Upperby the Eyni plateau, Ziyaret Hill and the Ayi andCretaceous (Fig. 10) (Erguvanli, 1963; Erguvanli,Kimil mountains. The detached masses of the1966). The first investigations of the Ataturk damKimil mountains are prominent in the scenery.site were started in the 1960s. On different dam-The glide masses of the third step butts againstsites, borings and tunnel investigations and thenthe second step and these would have moved aftergrouting tests were made. Finally, the current damthe sliding of the first step.axis was chosen, although it was larger and theEighteen numbered concrete poles were sunk atdam volume greater than the initial plans becausethe critical points of the Tillo, Bego and Senketothis axis was the most effective in reducing waterlandslide areas and these were geodetically sur-leakage.veyed during their motion. Movements to the NW

The oldest rocks on the damsite are dolomiticare quicker in the vicinity of Bego; those at thelimestone. Above the dolomitic limestone, thereSenketo territory are comparatively much slowerare bituminous and cherty lensing limestone.and also diversely directed. The values of the latterAbove this, there are plaquette limestone andstay within the limits of measurement errors.marls. Karababa Anticline is on the dam site andThe Rock Mechanics Laboratory at Istanbulhas an axis direction of NW–SE. On the SE limbTechnical University submitted the followingof the anticline, downstream, there are Bozovavalues for the samples from Gercus and Midyatand Ceviktepe faults which are parallel to eachformations: Gercus rock samples: C=26 kg/cm2,other. The faults’ net slip is about 400–600 m. The

w=48°; Midyat rock samples: C=75 kg/cm2, w=lowering SE block on Bozova fault caused dolomi-53°. These values are high as the samples weretic and plaquette limestone to exist next to the

taken from dry and sound rocks. Hence, theymarl. Secondary joints formed parallel and upright

would not be suitable for the stability to this system.computations. The dolomitic limestone on damsite is karstic

A core sample from the Gercus formation at a and pervious. Cherty and plaquette limestone are113.50–118.00 m interval of the SK-1 well, tested also karstic, but the argillaceous levels of limestoneat the above-mentioned laboratory, yielded the are impervious as is the marl above. Karstificationfollowing: Wp=19% and W=32%. The kneaded is manifest and dense on dolomitic limestone,but not consolidated sample yielded the following along bedding and joint systems. On plaquettevalues: qu=0.456 kg/cm2 and W=25%. A limestone, important karstifications have beenkneaded and consolidated sample under 1 kg/cm2 developed along faults. Secondary karstificationsload emplaced within the Casagrande box by have also developed along bedding planes andsudden cuts provided a value of Z$Cu= joints. On and around the dam site, there is0.380 kg/cm2. epithermal water below the aquifer, which has a

Samples were kneaded with water and subjected temperature reaching up to 24–26°C; the aboveto the minimum number of laboratory tests. More aquifer has a temperature of 15–19°C on bothrealistic values would be secured with tests over sides of the valley. Before the construction of thethe undisturbed core samples, especially if pre- dam, on the left side there was a small spring. Onserved with their original moisture content. As the right side of the dam, downstream there wassprings exist issuing from the contact of Midyat a spring with an undetermined capacity becausewith Gercus, this boundary plane would always of its disapperance into alluvium. Initially, it wasbe in a saturated state. Hence C and w values have thought that there would be no problem with theto be less than the given results of the laboratory dam site. However, even with a diversion tunnel

opening, a 1–1.2 m3/s capacity spring was seen.tests.


Fig. 10. Ataturk dam, view from downstream.

Its temperature was 24–26°C. In 1986, during the 10 m3/s when the reservoir level was 517 m. Whenthe maximum reservoir level is reached, the leakedopening of grouting galleries, new springs were

seen. While the level of the reservoir increased, water volume is expected to increase (Ertunc andCaynak, 1993).springs started to appear from the toe of the dam

(Fig. 11). On 1 November 1989, when the reservoir The most important thing which had not beenconsidered initially was that the epithermal springslevel was at 427 m, the spring’s capacity was

0.06 m3/s. On 25 February 1990, when the reservoir were at depths greater than 300 m, below the levelof grouting curtain, i.e. 180–200 m. Thus, thelevel reached 439 m, the capacity was 0.9 m3/s. In

February 1991, the reservoir level was 460 m and grouting curtain would not be able to prevent theleakage because the level of karstification wasthe capacity of the spring reached 1 m3/s. (see

Table 1) below that of the grouting curtain. As the reservoirlevel increases, the springs’ capacities increase andOriginally, because of the chemical characteris-

tics and the temperature of the water, it was the investigation boreholes’ pressures rise. On 24May 1990, fluorescein was injected into the PH-8thought that the water was not from the reservoir.

With the increase of the reservoir level, it was seen borehole and rhodomine B into the PH-12 bore-hole. Samples were taken from the downstreamthat this initial conclusion was wrong. On the dam

site, in tunnels, on the spillway, and on the toe of springs and boreholes and were analysed. As aresult of this, it was found that the velocity of thethe dam, water leakage started gradually increas-

ing. On the right side of the valley, about 2 km ground water of dolomitic limestone was morethan in the plaquette limestone. The ground waterdownstream of the dam, the first small spring

appeared and with its capacity increasing gradually flowed under the grouting curtain, which wasimpossible to prevent as the grouting curtain couldas the reservoir filled. In order to decrease the

pressure of the leaked water, drainage tunnels were not reach an impervious rock. Although groutinghad been completed on the R4 tunnel, fluoresceinbuilt downstream of the dam. In February 1993,

the total leaking water from the dam reached passed through this curtain, indicating that the


Fig. 11. Ataturk dam, springs started to form the toe of the dam.

Table 1Some piezometric measuremetns of the downstream boreholes

Borehole October October October October October October October Octobernumber 1989 1990 1991 1992 1993 1994 1995 1996

PH-9 (right side) 389.94 427.94 431.49 441.34 444.74 446.10 446.94 447. 02PH-12 (right side) 430.12 435.46 448.19 453.69 455.17 455.44 455.56PH-14 ( left side) 436.33 449.14 455.56 454.50 455.16 446.15PH-27 ( left side) 449.86 472.60 483.34 485.74 485.04 485.27PH-33 ( left side) 439.60 456.02 463.25 463.80 462.33 462.18Reservoir level (m) 397.33 451.94 484.47 511.29 528.67 534.50 534.48 534.74

grouting was not totally successful. Under the clay because of the karstification. The volume of waterleakage was reduced to 7–8 m3/s as a result of acore of the dam, extending 30–40 m below the

surface, high grouting pressure could not be new investigation and this amount remained con-stant. On the downstream side of the right slopeapplied. Thus, the water leaked through this part

of the grouting curtain with the amount of this of Karakaya dam, the Tillo–Bego–Senketo land-slides have been an important risk to the dam. Ifleakage being immeasurable.these landslides cause an artificial lake by blockingup the Euphrates River, the Karakaya powerstation could be flooded. The total volume of5. Conclusionsleaked water from the Ataturk damsite and itsvicinity reached at least 10 m3/s when theWhen the Keban reservoir was filled,

26–30 m3/s of water leaked from the Keban Creek reservoir level was 517 m. When the reservoir is


Erguvanli, K., Kumbasar, V., 1967. The Geological and Soilfull (542 m) the volume of leaked water is expectedMechanical Studies of the Landslides at the Vicinity of theto increase.Karakaya Damsite on the Euphrates River (in Turkish).Special Report of the EIE, Istanbul, Turkey.

Ertunc, A., Hadimli, L., 1971. The Geological Investigation ofthe Left Reservoir Rim of Keban Dam between Murat RiverReferencesand Keban Creek. EIE Report (in Turkish), Ankara, Turkey.

Ertunc, A. et al., 1972. Keban Project Investigation of PossibleBozovic, A. et al., 1972. Report of Left Reservoir Rim Leakage Leakage Courses from Left Reservoir Rim. EIE Report,

Problems at the Keban Dam Site. EIE Publication no. 72-35, Ankara, Turkey.Ankara, Turkey. Ertunc, A., Caynak, S., 1993. Hydrogeological investigation of

Erguvanli, K., 1963. Geological Investigations of the Halfeti the Ataturk dam. International Symposium of ExploitationDam’s Reservoir on the Euphrates River (in Turkish). of Mineral Resource Deposits and Underground Construc-Special Report of the EIE, Istanbul, Turkey. tion in Complicated Hydrogeological Conditions, Belg-

Erguvanli, K., 1966. The Damsite Possibilities between Halfeti orod, USSR.and Findikli on the Euphrates River and Geological Proper- Kosar, E., 1981. Final Report of Grouting Curtain of Leftties of their Reservoirs (in Turkish). Special Report of the Reservoir Rim at the Keban Dam Site. EIE Publication no.

81-37, Ankara, Turkey.EIE, Istanbul, Turkey.

Documents

01 Önemli Cave