and support recommendations for the encountered rock types. R6sum6. L'article prrsente la ..... Crown : Systematic unstrained bolting has 3 m lengtb, intervals. 15 cm thick ... medium-heavy steel rigs every 0.75 m. Wall : No support needed.
BULLETIN
GEOTECHNICAL TURKEY
of the International Associationof ENGINEERING GEOLOGY
de I'Association Internationale de GC:OLOGIE DE L'INGC:NIEUR
INVESTIGATIONS
Paris
OF I~IKLI TUNNEL ALTERNATIVE
-
No 53 -
Avril 1 9 9 6
ALIGNMENTS,
t~TUDE GIS,O T E C H N [ Q U E DES DIFFI~RENTS TRACt~S P O S S I B L E S P O U R L E T U N N E L D ' I ~ I K L I , TURQUIE
6 Z G U L E R E.*, ERTUNC A.**, T A N E R O.***
Summary The regional geology of the alternative tunnel alignments of I,~ikli Tunnel and its decisive influence on alignment of different alternative waterways is presented. A solution with optimum use and possible most favorable tunneling conditions were established. A procedure including rock mass classification and subsequent study of alternatives was used. Results are given for the NGI (Q), CSIR (RMR) and RSR systems for rock units as well as the signification and support recommendations for the encountered rock types. R6sum6 L'article prrsente la g~:ologie rrgionale du Tunnel d'I}ikli, en Turquie, et son influence sur les tracrs possibles. On a mis au point une solution combinant une utilisation optimale et des conditions de foration des tunnels les plus favorables possibles. La mrthode utilisre inclut une classification des massifs rocheux puis une ~tude des variantes. Les r(:sultats sont prrsentds dans le syst/~me NGI (Q), CSIR (RMR) et RSR pour des ensembles rocheux et complrtds par des recommandations pour chaque type de roche traversre.
1. I n t r o d u c t i o n The location of the project area, located between the Western Black Sea Region and Central Anatolian Region and approx. 150 km northwest of Ankara, is shown in Figure 1. At present the amount of water supplied to Ankara is 307 x 106 m3/year. Also t40 x 106 m~/year water will have been supplied by the end of 2002. However after 2002 new sources of water will have to be found when population growth statistics are taken into consideration. The idea of diverting water from I~ikli Dam, thought to be one of new sources, located in the Western Black Sea Basin to ~amlidere Dam reservoir, located in the Sakarya Basin, appears as the best alternative. Both Ankara city and (~amlidere Dam are located in the Sakarya Basin.
GEREDE
~DERE H~tAP
Although head is available between these two basins, diversion without a tunnel or pumping is impossible due to the Kt~roglu Mountains. 322 x 106 m3/year water will be diverted to ~amlidere Dam reservoir from I~ikli Dam via the transmission system and the tunnel. This amount of water is thought to be sufficient for Ankara until the end of 2020. The proposed system, shown in Figure 2a, b and c, has four alternatives. I~ikli Dam is existent in all alternatives. Transmission system has cut and cover galleries and pipelines in
* General Directorate of State Hydraulic Works, Ankara, Turkey. ** University of ~ukurova, Faculty of Engineering, Adana, Turkey. *** 5th Reg. Direc. of Gen. Direc. of State Hydraulic Works, Ankara, Turkey.
tO i
SCALE : 0 ~0
Fig. 1 : Location Map.
I
*
I
km.
74 [$IKLI DAM
I~IKLI DAM
cuandco~m oaller~
L=53,~Om. C-eCit~r $cn'~
"laetlar
~ipeline(L=8250)
,i ~ Pipeline(L.=Sb-P3) Short tunnel
L=IOCCm.
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(L:5~m) I~ All. [. Maintunnel ~'~=d'k\ L: 16ooo) _ mGJn tunne{
Bt~ral?r
(•AAIt.2 L= 9C~COm.
y
.
Unsealed
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\ Fig. 2a : General Layout of AIternative 1.
Fig. 2b : General Layout of Alternative2.
variable lengths. Also there are pumping stations, which have variable pumping head. The tunnel will be presented because it is considered as the most important structure in the system...
In order to establish a sequence, it was necessary to judge the geological and geotechnical conditions along the alternative tunnel alignments. The aim of the study is to determine the geological and geotechnical features, to apply the rock mass classifications and to decide the support system of alternative tunnel alignments of I~ikli Tunnel.
Alternative 1 has the longest tunnel with 16800 m in length. Alternative 2, 3 and 4 are named as higher pumping alternatives having 9 000, 5 000 and 2 500 m tunnel lengths respectively. Additionally Alternative 2 is divided into two sub-alternatives. One has 9 000 m tunnel length and access adit possibilities. The other one has 9 400 m tunnel length and shaft systems.
3. C o l l e c t i o n o f
data
The feasibility design considered the following geological and geotechnical field and laboratory investigations - - Aerial photo interpretation.
2.
Methodology
The design procedure of tunneling was characterized by the following steps : --
Collection of data.
Definition and optimization of selected alternatives under geotechnical consideration.
--
Based on the results of geotechnical investigations rock quality indices were attached for each lithological unit. The classification methods used were the RSR, the CSIR (RMR), the NGI (Q), rock quality indices, the first defined by Wickham, Tiedemann and Skinner (1972), the second by Bieniawski (1979, 1989) and the third by Barton, Lien and Lunde (1974).
- - Geological mapping. --
Investigation drillings.
- - Hydrogeological evaluation. --
Statistical determination of discontinuities.
Determination of material parameters like uniaxial strength, elasticity modulus and Poisson's ratio.
--
3.1.
Lithostratigraphy
The area is constituted mainly by volcanics. Old tO young Aktas formation, Btinias formation, Hacilar formation, K6ro~lu volcanics and Geqitler formation, have been located in the area (C)zgtiler, 1994).
75
Hacilar formation
I$1KLI N
, ( ..~] | Pil~li~ (L=82~)
The succession of Hacilar formation begins with basal conglomerate. Then the grain size gets finer. Sorting and gradation are not observed. Fine grained sandstones have hard, coarse grained sandstones have weak strata. Silstone intercalations also existed. Fresh surfaces are beige, as minerals components labrador, biotite, quartz, hornblend and opaque minerals; as rock fragments andesite, limestone and chert are observed. This unit has fossils which characterize the shallow sea and aged Upper Eocene.
St~et tumgl
Kbrter
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u ns~ll~l
K6ro~glu volcanics Different rock units in K6rog, lu volcanics have vertical and horizontal transition. Generally Salur lava is observed at bottom. Andesite, basalt, trachyte, tuff and trachyandesitic vitric tuff can be distinguished. Existence of trachyandesitic vitric tuff has the most important disadvantage in the process of judgement of the alternative alignments. This unit was formed by quick cooling. Samat agglomerate overlays Salur lava. Karapazar lava is made up of blocky andesite ; basalt overlays all.
Salur lava
Fig. 2c : General Layout of Alternatives 3 and 4.
The lithostratigraphic column in Figure 3 summarizes the rock formations. Figure 4 presents geology of the four alternatives.
Salur lava is formed of andesite, basalt, trachyte, tuff and trachyandesitic vitric tuff. Trachyte is grey, beige, hard and stiff, also cracky and jointed. Basalt and andesite are not observed as an outcrop. Basalt is grey, black, blocky, vitrified and has amiadoloidal structure. Andesite is grey, hard, stiff and blocky. Tuffite is white, grey and alterated. Vitric tuff is yellow, white, decomposed and vitrified. According to X Ray Diffraction Analysis vitric tuff has 50 % to 100 % montmorillonite minerals.
Samat agglomerate A ktas formation Represented in two facies. Horizontal and vertical transitions exist between them. Thick bedded limestone is dominant in the study area. Through the Eastern parts of the area limestone-sandstone intercalation outcrops can be seen. Limestone is white, hard, jointed and oolithic. Sandstonelimestone intercalation is grey-white and jointed. This unit aged as Upper Jurassic-Upper Cretaceous (1)nlti, 1973).
Biiniis formation Basal conglomerate is located at the base of Btintis formation and lava-limestone intercalations overlay it. Limestone has dark grey and white colour. Fresh surfaces are light grey and white. It is also hard, easily brittled; some parts are laminated and cracky. Lava has been formed as crack eruptions and is vitrified. Pillow lava can't be seen. Metamorphism can't be observed for limestones due to the temperature decrease. Vitric structure also confirms the sudden cooling. This unit has fossils which characterize the deep sea and aged as Lower Eocene.
Bottom parts can be defined as volcanic conglomerate. Reddish tuff intercalations also exist. Through the upper parts tuff content in matrix is incrased. Biotite, oligoclase, andesine can be observed as minerals; reddish lava, tuff, fillite, biotite schist, quartzite and microgranite are seen as rock fragments.
Karapazar lava Made up of andesite and basalt. The unit is wholly sliced and jointed; fresh surface of basalt is dark grey, black, brown and more cracky and blocky, hard and stiff. Andesite is yellowish, beige coloured, hard and stiff. Andesite is formed as augite andesite, hornblend a n d e s i t e basalt is formed as hornblend-augite basalt. Both basalt and andesite chloritization is dominant.
Gefitler formation Made up of unconsolidated sand and gravel having horizontal strata. Tuff, chert, reddish lava fragments can be seen. Sorting and gradation are not observed. Roundness is worse.
76
ERA
SYSTEM
SF_.I~IES
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ouater -
FORMATION AllUVium
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Consists 0f c:oarse pebble and silty unconsolidated materiel UNCONFORMITY Her ~ontal bedded,semimns~ldated gr~l,send,sdt,~tey UNCONFORMITY Andesile:Beige-grey,sllced,stiff hard.Basalt.Beige,grey,black, creePy,so'he parts Pk~cky. UNCONFORMITY Cor~i~ts of rounded lave,tuff, fillite,mqcrogranite,schist fregrnent~End lave InterC:aletions An0eslte: Grey,stiff, blocKy. BasaR:Grey,bleck,blouky,gasporec Tutt:Tellow, wtllte,brltt=e,vltrltled. Tranhyte: Beige,grey j~ntad,hard UNCONFORMITY Flysch:.Sendstone;beige.so~art~ fine,ethers co~rse grained. ! Conglomerate Bedding,sorting ant gradeti~'~ not ex~ted,h~s volcanic rock rragments. UNCONFORMITY I ave-l~mestone inter(elations Limestone:Grey wt~ite, brit tie, hard Lava formed as severe crack empt~n TECTONIC BOUNOARY L#nestane.Thick bedded,white,her Jointed and Oollthlc. Sandstone-limestone Inter~latlens: Thick bedded,grey,w~ite Jointed.
Fig. 3 : Generalized stratigraphic columnar section of Isikli tunnel alternative alignments.
3.2. Structure Two fault systems have developed in the study area. One has NE-SW strike, has less extension and is older than the other group. The other group has NW-SE strike and is younger than the first group. All faults have developed in different ages by the effect of North Anatolian Fault Zone. During the tunnel excavation, in addition to 13 faults determined from aerial photos and field observation (K0kti0z, 1986, Ozgtiler, 1994), many covered faults buried by serial volcanic activities, can be seen. 4. E n g i n e e r i n g G e o l o g y Target of the investigations was to find the alignment, which shows an optimum regarding minimum length and best geotechnical conditions. Figure 5, 6a and b, 7, 8 present the longitudinal profile of tunnel of Alternative 1, 2a and b, 3, 4. A number of tests have been performed in order to determine the physical, mechanical and geotechnical properties of the rock units which may be seen during the tunnel
excavation. According to X Ray Diffraction Analysis the rock unit named trachyandesitic vitric tuff has 50-100 % montmorillonite. Core samples of trachyandesitic vitric tuff are very stiff and hard but if they are put in water they disperse wholly (Taner, 1993). Physical, mechanical and geotechnical properties of the rock units which may be penetrated during the tunnel excavation are as follows : Andesite, basalt and trachyte have low-medium strength, low alteration, fleshy clay fill and are classified as medium hard rock. Agglomerate has very low strength, tow alteration, fleshy clay fill and is classified as weak rock. Tuff has very low strength, medium-high alteration, soft clay fill and is classified as very weak rock. Limestone has medium-high strength, low alteration, fleshy clay fill and is classified as hard rock (Table I). The test results and field observations are taken into consideration to perform RSR, RMR and Q Tuck mass classifications (Wickham et aI., 1972), (Bieniawski, 1979, 1989), Barton et al., 1974). Both an optimistic and a pessimistic evaluation have been performed in order to determine the rock quality indices of each rock unit. The summerized
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