THE PERFORMANCE OF TWO EPB MACHINES IN ISTANBUL METRO TUNNEL DRIVAGES IN SOFT AND SHALLOW GROUND

THE PERFORMANCE OF TWO EPB MACHINES IN ISTANBUL METRO
TUNNEL DRIVAGES IN SOFT AND SHALLOW GROUND
Ibrahim Ocak1, Nuh Bilgin2
1

Istanbul Metropolitan Municipality, IETT General Directorate, Rail Transport Construction
Manager, Karakoy/Istanbul-Turkey,
2
Istanbul Technical University Faculty of Mines, Mining Engineering Department, Ayazaga
Campus, Maslak/Istanbul-Turkey,

Keywords: Tunnel excavation, machine utilization time, EPBM.

ABSTRACT
The prediction of machine utilization time and determination of machine performance plays an
important role in scheduling and planning tunnel excavation and data base created serve a major
role in further applications.
In this study, the construction methods of two twin tunnels situated within Kirazlı1- Esenler Metro
line are summarized. Geology in the study area is composed of sediment fillings, stiff clay, dense
sand, very dense sand, and hard clay, respectively starting from the surface. The tunnels of 5.8 km
in length are excavated with two different EPB Machines of 6.5 m in diameter. The performance of
the machines are analyzed and compared in order to accumulate data for further applications in
similar ground conditions in Istanbul.
The distance between two twin tunnels is 14 m from center to center and the EPBM in the right tube
is almost about 100 m behind the other tube. Segmental lining with 1.4 m of length is currently used
as final support.
The overall performances of Herrenknecht EPBM and Lovat EPBM are found to be respectively as;
the best daily advance rates 25.2 (18.1.2007) m/day and 23.8 (31.1.2008) m/day, the best weakly
advance rates 102.2 m/day and 118.5 m/day, the best monthly advance rates 415.9 m/day and 418.6
m/day, the mean daily advance (including waiting due to excessive deformations) 5.6 and 5.4
m/day, the mean daily advance (excluded waiting ) is 11.1 and 11.3m /day respectively Waiting

time due to excessive ground deformations is 29.3 % and 27.7 % respectively.

INTRODUCTION
Underground constructions in the world are steady increasing for different purposes like, metro,
sewerage, irrigation tunnels, and for storage of different materials. This increasing trend is expected
to be in the favor of mechanized tunneling with TBM’s in hard rock and EPB’s in soft ground. The
main advantages of using mechanical excavators compared to drilling and blasting method may be
cited as, less vibration is encountered in the surface, less surface settlements are expected,
maximum labor safety is obtained and less breakout minimizes the support requirements. In
Istanbul it is experienced that the use of mechanized tunneling is more favorable than using NATM.
The first construction of the Istanbul Metro began in 1992 and opened to the public in October
2000. Nowadays, five Istanbul Metro lines have been constructed. One of these lines, OtogarKirazlı 1 Metro, was excavated between Esenler and Kirazlı 1 and consists of five stations. The
Otogar- Kirazlı 1 Metro line is under construction by a Gülermak- Doğuş joint venture.
The accumulated data in different tunneling project in Istanbul is expected to serve a basis to plan
and coordinate more efficient tunneling applications. This paper is prepared in this respect.
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Excavation and support
The first construction phase of the Istanbul Metro line began in 1992 and opened to the public in
2000. This line is being gradually extended, and additional tunnels are being constructed in other
locations. One of these metro lines is the twin line between Otogar and Kirazlı 1, a 5.77 km. Metro
line consisting of a 3.87 km tunnel, a 0.62 km cut and cover station, and 1.28 km at grade crossing.
The excavation of this section began in May 2006 and was completed in June 2008. This metro line
will integrate the Kirazlı 1- Başaksehir- Olimpiyat Köyü Metro Project that is currently under
construction and is 15.8 km in length. At the same time, the Otogar and Kirazlı 1 Metro Line will
integrate the Aksaray- Ataturk Airport light metro line that is now under service (Fig. 1).

Başakşehir

European Side

Olimpiyat
köyü
Güney sanayi
Bosphorus
Otogar
Kirazlı 1

Halkalı

Atatürk
Airport

Anatolia Side
Golden Horn
Aksaray

Bakırkoy IDO

Marmara Sea
0 km

5 km

Figure 1. Main route of Otogar- Kirazlı 1 Metro line and location.

A total of 2 EPBMs are used for excavation of the tunnels (Fig 2). The metro lines in the study area
were excavated by a Herrenknecht EPBM in the left tube and a Lovat EPBM in the right tube. One
tube excavation has followed around 100 m behind the other tube. Some of the technical features of

the machines are summarized in Table 1.
Excavated material is removed by an auger (screw conveyor) through the machine to a belt
conveyor and then loaded into rail cars for transporting to the portal. Since the excavated ground
bears water and includes stability problems, the excavation chamber is pressurized by 300 kPa and
conditioned by applying water, foam, bentonite, and polymers through the injection ports. Chamber
pressure is continuously monitored by pressure sensors inside the chamber and auger. Installation of
a segment ring with 1.4 m length (inner diameter of 5.7 m and outer diameter of 6.3 m) and 30 cm
thickness is realized by a wing type vacuum erector. The ring is configured as five segments plus a
key segment. After installation of the ring, the excavation restarts and the void between the segment
outer perimeter and excavated tunnel perimeter is grouted by 300 kPa pressure through the grout
channels in the tailing shield. This method of construction is proven to minimize the surface
settlements.

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(a)
(b)
Figure 2. Tunnel boring machines; (a) Herrenknecht (b) Lovat.
Table 1. Some technical features of the EPBMs.

Excavation diameter (m)
External diameter (m)
Internal diameter (m)
Segment thickness (m)
Average segment length (m)
Configuration of segment
Shield outside diameter (m)

TBM length (m)
Backup length (m)
Total weight (tones)
Maximum cutter head (rpm)
Total installed power (kW)
Face pressure (kPa)
Cutter head type
Cutter head power (kW)
Maximum torque (tm)
Maximum thrust (kN)
Belt discharge capacit. (m³/hr)
Grout output

Herrenknecht
6.500
6.30
5.70
0.30
1.40
6 (5 + 1 keystone)
6.45
7.68
80
578
0 – 2.5
963
300
Mixed ground
630
435 (2.5 rpm)

32
450
Grouting the tailing shield

Lovat
6.564
6.30
5.70
0.30
1.40
6 (5 + 1 keystone)
6.52
9.30
65
534
0 – 6.0
1622
300
Mixed ground
900
445 (1.9 rpm)
54
720
Grouting the tailing shield

The Geology of the study area
The study area includes the twin tunnels between Otogar and Kirazlı 1 stations. The Güngören
Formation of the Miosen age is found in the study area. Laboratory and in-situ tests are applied to
define the geotechnical features of the formations that tunnels pass through. Some of the
geotechnical properties of the layers are summarized in Table 2 (Ayson, 2005). The sediment

fillings consist of sand, clay, gravel and some pieces of masonry. The sand layer is brown in upper
levels and greenish yellow in lower levels, consisting of clay, silt and mica. Very dense sand is
greenish yellow and consists of mica. Clay layer is grayish green in color and made up of gravel
and sand. The base layer of the tunnel is hard clay that is dark green and consists of shell.
Underground water table starts about at 4-5 m below the surface at the study area. Tunnels are about
10-40 m below from the surface. The geology of the study area is given in Figure 3.

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Table 2. Some geotechnical properties of the study area (Ayson, 2005).

Unit weight
(kN/m3)

Strata
Fill
Sand
Very dense sand
Clay (Güngören fr)
Hard clay (Güngören fr.)

18.0
18.3
18.5
16.5
17.2

Modulus of
Elasticity
(kN/m2)
5,000
25,000
30,000
20,000
28,000

Cohesion
(kN/m2)

Poisson
ratio

Angle of
Friction

1
1
1
20
25

0.30
0.25
0.30
0.35
0.40

10
35
30
14
20

80
70
6
50
4
30
2

Fill
Clay
Sand
Trakya formation
Metro line

1
Kilometer

0+000
0+500
Structure Type Viad. At Grade R.W

0m
1+000
Bored Tunnel

1+500
Cut&
Cove

2+000
Bored Tunnel

2+500
Cut&
Cove

250 m

3+000
Bored Tunnel

3+500
Cut&
Cove

4+000

4+500
Bored Tunnel

Cut&
Cover

Figure 3. The geology of the study area (Ocak, 2009).

PERFORMANCE OF THE EPBMS
The tunnel excavation in study area started in May 2006 and finished in June 2008. The
performance of EPBMs were recorded during about two years. The summary of the EPBMs
performance is given Table 3 and Figure 4.
Table 3. Overall performance of the EPBMs.

Excavation started time
Excavation finished time
Excavated tunnel (m)
Total study time (day)
EPBM working time (day)
EPBM waiting time (day)
Percentage of waiting for deformation
The best daily advance (m/day)
The mean daily advance (m/day) (including waiting due to
excessive deformations)
The mean daily advance (m/day) (excluded waiting)
The best weakly advance (m/week)
The best month advance (m/month)

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Lovat (Right
tunnel)
01.04.2006
20.05.2008
4253.3

780
564
216
27.7
23.8 (31.1.2008)

Herrenknecht (Left
tunnel)
13.05.2006
04.06.2008
4219.7
753
532
221
29.3
25.2 (18.1.2007)

5.42

5.59

11.28
118.54
(1-7 Oct. 2007)
418.60
(September 2007)

11.09
102.2
(12-18 Nov. 2007)

415.88
(August 2007)


Kilometers

4+500
4+000

Lovat (Right tunnel)

3+500

Herrenknecht (Left
tunnel)

3+000
2+500
2+000
1+500
1+000

2008-05-13

2008-03-13

2008-01-13

2007-11-13

2007-09-13

2007-07-13

2007-05-13

2007-03-13

2007-01-13

2006-11-13

2006-09-13

2006-07-13

0+000

2006-05-13

0+500

Date

Figure 4. Excavation performance of the EPBMs.

As can be seen from Figure 4 two EPBMs waited for almost nine months in three regions due to
ground and tunneling problems, i.e. poor ground conditions (clay or sand-clay), shallow depth,
interference of twin tunnels and week structural problems of the buildings in the tunnelling area
(Ocak, 2009).

A typical deformation curve in a critical zone is given in Figure 5 Deformations start when the first
tunnel approaches the surface measurement point (SMP) and building measurement point (BMP)
and steadily increase up to measurements points. The actual deformations that occur both at the
surface and in the buildings are formed when second EPBM comes to the area passed through and
disturbed by first EPBM and later on both deformations stop. Figure 5 shows the change of the
surface settlements in a sample point according to the EPBM positions (Ocak, 2009).
0

320
Settelement
Lovat
Herrenknecht

240
160

-60

80

-80

0

05.09.06

16.08.06

27.07.06

07.07.06

-160
17.06.06

-120
28.05.06

-80

08.05.06

-100

Date

(a)
Figure 5.

Distance from tunnel face (m)

-40

18.04.06

Surface settelements (mm)

-20

SMP measurement point

14.42 m

fill

clay

Right tunnel
Lovat

Left tunnel
Herregnet

8m

sand

6.3 m

(b)

(a) The relationship between surface settlement and EPBMs position in relation to a SMP
measuring point at km 0+879 (b) Position of SMP at km 0+879 (Ocak, 2009).

During tunnel excavations, 28 buildings with 214 flats were evacuated and demolished because of
the severe damage occurred due to high surface deformations. In addition to the demolished
buildings, a total of 364 flats were also evacuated due to safety reasons and the, rent and removal
expenditures were also paid off. Demolishing and repairing buildings, rent payments, and other
5

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expenses totaled 35.6 million dollars which increased the project cost up to 15.8 %,. the total initial
project cost being 225 million dollars. (Ocak, 2009). The cost of
standby of EPBM without excavating, including the cost of the staff, energy consumption, taxes and
site expenses should also be added to the number given below
CONCLUSIONS
Tunnel excavation in Esenler-Kirazlı 1 started in May 2006 and finished in June 2008. The main
ground formations excavated were fill, sand and clay. Geologic structure of area can be classified as
soft ground. Tunnel depth is 14-40 m. In this study, EPBMs performances were examined for twin
tunnels which are excavated between the Otogar and Kirazlı 1 stations of the Istanbul Metro Line.
Tunnels, with 6.5 m in external diameters and 14 m distance between their centers, were excavated
by two EPBMs.
The mean monthly advance rate of 4.2 km for Lovat and Herrenknecht EPBM were obtained 418.6
m and 415.88 m respectively. The mean daily advance rate for Lovat and Herrenknecht EPBM were
as 11.28 m and 11.09 m respectively. High surface deformations obtained in three regions caused
severe damages to the surrounding buildings which were evacuated and demolished thereafter.
Some of the buildings were also evacuated due to safety reasons. All these extra activities cost
almost 35.6 millions dollars which increase the cost of the project up to 15.8%. These experiences
strongly emphasizes that tunneling in shallow depth in urban areas needs detailed side
investigations including detailed research studies in order to minimize the cost of tunneling.

REFERENCES
Ayson Drill Research and Build. AS, (2005), Otogar-Bağcılar Station Geological Geotechnical Report (in Turkish).
Ocak, I., (2009), “Environmental Effects of Tunnel Excavation in Soft and Shallow Ground with EPBM: The Case of
Istanbul”, Environmental Earth Science (in press).

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