Evaluation of machine utilization time and performance of EPB TBMs used in Atakoy –Ikitelli metro tunnel project

In this thesis, the performance of the TBMs used in Ataköy – İkitelli metro tunnel project is evaluated, and dominant factors influencing the machine utilization are examined. The progress of the worksite was followed personally from the beginning of the assembly of the machines to construction on site. The effect of geological conditions on machines performance is investigated via performance analyses and interpretation of the project outputs. Thus, the advance rates of four TBMs are compared within three different geological formations in Istanbul. Besides, site management and scheduling related issues are determined based upon shift and machine reports, and then the reasons of the scheduled, non-scheduled and operational stoppages are analyzed. Despite identical specifications of the TBMs, main differences on utilization durations and performance of the TBMs are compared between the two TBMs, which excavated through the parallel tunnels in the same direction. As a result of this study, an increase in average torque values was observed within the sandy soil (Çukurçeşme Formation) in the direction of Ataköy station due to the higher friction coefficient of sand, and under these circumstances, advance speed of the TBMs decreased considerably, while utilization per ring increased inefficiently. The average torque and thrust force values increased significantly depending on the soil properties within the clayey soil (Gürpınar Formation) in the direction of İkitelli station. When required specific energy to excavate unit volume of clayey soil and advance rate are taken into consideration, the most efficient excavation is obtained within Güngören Formation, which has the lowest standard penetration test value (N30) and favorable soil properties. Additionally, the advance rate of the TBM, which was driven in the behind of the first one, is lower within the clayey soil in contrast to values received in advance speed within sandy soil especially in the direction of Ataköy station. On the other hand, crucial significance of effective scheduling and site management at the beginning of the project is proven by considering the effect of the encountered problems on the machine utilization rate during the progressive stages of the project. It is clearly shown that the machine utilization rate increased remarkably when the long shaft preparation and waiting periods are excluded. Detailed machine utilization time analysis of S-1031 is carried out, and the result shows that MUT increased from 22% to 30% when these long stoppages are eliminated. The time losses were experienced due to challenging geological conditions, and this situation decreased MUT during the construction of the tunnel. In contrast to the most efficient MUT at 28% for S-1030, it is shown that S-1029 has the lowest MUT at 13% because of such time losses.