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 Ocak 1 , Nuh Bilgin 2 1 Istanbul Metropolitan Municipality, IETT General Directo

THE PERFORMANCE OF TWO EPB MACHINES IN ISTANBUL METRO

TUNNEL DRIVAGES IN SOFT AND SHALLOW GROUND

Ibrahim Ocak 1 , Nuh Bilgin 2

1

Istanbul Metropolitan Municipality, IETT General Directorate, Rail Transport Construction

Manager, Karakoy/Istanbul-Turkey, iocak@iett.gov.tr

2

Istanbul Technical University Faculty of Mines, Mining Engineering Department, Ayazaga

Campus, Maslak/Istanbul-Turkey, bilgin@itu.edu.tr

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, Otogar-

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)

Marmara Sea

Aksaray Otogar

Başakşehir

European Side

Anatolia Side Bosphorus

Bakırkoy IDO Halkalı

Olimpiyat köyü Güney sanayi

Atatürk Airport

Golden Horn Kirazlı 1

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

Figure 2 Tunnel boring machines; (a) Herrenknecht (b) Lovat

Table 1 Some technical features of the EPBMs

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

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

(kN/m3)

Modulus of Elasticity (kN/m2)

Cohesion (kN/m2)

Poisson ratio

Angle of Friction

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

Lovat (Right tunnel)

Herrenknecht (Left tunnel)

The mean daily advance (m/day) (including waiting due to

(1-7 Oct 2007)

102.2 (12-18 Nov 2007)

(September 2007)

415.88 (August 2007)

0+000 0+500 1+000 1+500 2+000 2+500 3+000 3+500 4+000 4+500 Viad At Grade R.W Bored Tunnel Bored Tunnel Bored Tunnel Bored Tunnel

1

2

30

4

50

6

70

80

Cut&

Cove

Cut&

Cove

Cut&

Cove

Cut&

Structure Type

Kilometer

Fill

Clay

Sand

Trakya formation

Metro line

0 m 250 m

0+000 0+500 1+000 1+500 2+000 2+500 3+000 3+500 4+000 4+500

Lovat (Right tunnel) Herrenknecht (Left tunnel)

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)

-120

-100

-80

-60

-40

-20

0

Date

-160 -80 0 80 160 240 320

Settelement Lovat Herrenknecht

14.42 m

6.3 m

8 m

Left tunnel Herregnet

Right tunnel Lovat SMP measurement point

sand

fill

clay

Figure 5 (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

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)