1 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- Kirazlı 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- Doğu 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.