عنوان مقاله [English]
One of the most important issues in mechanized tunneling specially in the urban areas is selection of the suitable boring machine. Geological and geotechnical conditions, soil type and variations, underground water level, site location and urban conditions are important parameters that influence the machine type and excavation method in the urban areas. In this paper in addition to the mentioned parameters the performance of mechanized machines and guidelines of the machine selection is assessed for Tehran Metro Line7 tunnel (East-West part). East-West tunnel is located between Takhti Stadium, A7 station in the east of Tehran and N7 station in Navvab-Safavi highway. The tunnel boring diameter is 9.15 m and tunnel length is 12360 m. According to geological studies the ground soil is divided into four types based on the soil type, grain size distribution and geotechnical conditions. The divided types cover wide range of the soil from clay to sand. Also more than 60 % of the tunnel length is located blow the underground water level. Various parameters such as tunnel route, soil type, site conditions, underground water level, project time schedule and different shield machines performance and limitations have been considered for machine selection. Among the different shield machines in the soft ground, EPB type shield machine is chosen as a suitable tunnel boring machine for the project. In addition to required auxiliary equipment, lower excavation costs and higher performance, the EPB type machine is a suitable option in comparison to other shield machines based on the project soil type. The EPB shield has priority over other shield types due to range of applications and excavation in different mode (open, EPB, slurry); therefore this type is recommended for the project.