Geotechnical risk data analaysis and evaluation of urban EPB tunnel projects based on geological formations

In the thesis, the Tunnel Boring Machine (TBM) technology, a significant aspect of tunneling engineering, plays an indispensable role in modern infrastructure projects. This study presents a comprehensive analysis aimed at optimizing tunneling excavation processes, focusing on TBM technology and particularly the performance of Earth Pressure Balance (EPB) TBMs. The initial sections of the study delve into the theoretical foundations of TBM technology, methods for calculating face pressure, and the impact of these methods on tunneling performance in detail. Additionally, critical approaches such as risk management and probabilistic analysis methods are evaluated in both theoretical and practical contexts. In subsequent sections, the effects of geotechnical and hydrogeological conditions on TBM performance are analyzed using the Ataköy-İkitelli and Halkalı-New Airport metro lines as examples. The results provide actionable solutions aimed at improving excavation processes and effectively managing risks in large-scale tunneling projects. The second and third sections of the study provide a theoretical foundation by detailing fundamental knowledge on tunneling methods and TBM (Tunnel Boring Machine) technology. Specifically, the methods for calculating face pressure in EPB (Earth Pressure Balance) TBMs, the formulas employed, and the impact of these calculations on tunneling performance are thoroughly discussed. These sections contain critical theoretical insights essential for optimizing TBM excavation processes and improving performance. Furthermore, terminological explanations regarding risk concepts and probabilistic methods, along with a detailed examination of various risk analysis methods, form an important part of these sections. By addressing risk assessment approaches both within a theoretical framework and through practical applications, the study establishes a robust methodological foundation. These sections integrate academic knowledge in tunneling and risk management with practical applications, creating a scientific basis for the study. The fourth and fifth sections examine the geotechnical and hydrogeological characteristics of the Ataköy-İkitelli and Halkalı-New Airport metro lines and evaluate the effects of these characteristics on Tunnel Boring Machine (TBM) excavation performance. Within the scope of the study, laboratory and field tests conducted in different formations are comprehensively analyzed. Additionally, the differences and similarities among calculation methods for EPB face pressure values are statistically evaluated, and a risk assessment is performed using the 5x5 L-Type Matrix Method. These analyses provide critical insights into risk management strategies for large-scale tunneling projects. According to the obtained results, the geotechnical conditions have demonstrated a significant impact on TBM performance. On the Ataköy-İkitelli Metro Line, unit weight and water content were found to have a significant effect on EPB pressure values. On the Halkalı-New Airport Metro Line, unit weight and plastic limit were identified as significant factors influencing excavation performance. Furthermore, the role of hydrogeological challenges in tunnel excavation was examined in detail. Comparisons made between the metro lines provided insights into the effects of varying ground conditions on excavation efficiency. Regression analyses for EPB pressure calculations led to the development of model proposals, which were validated by comparing their accuracy with the literature. In conclusion, the study offers practical recommendations for optimizing tunnel excavation processes and minimizing risks. In conclusion, this thesis emphasizes the importance of preliminary and detailed geological investigations in the tunneling sector. Aiming to minimize discrepancies between design and implementation, the study seeks to enhance the understanding of the effects of geological parameters on tunnel boring machine performance. The knowledge gained is expected to contribute to future projects and improve engineering practices in the industry.