Abstract: Various difficulties are encountered in sand-pebble strata, which are typically mechanically unstable, and serious tool wear has been experienced during shield tunneling. The cutterhead selection and tool arrangement are the key to realize the long-distance and efficient shield driving in sand-pebble strata. Taking second section of the Beijing New Airport line tunneling project as background, this paper studied the influence of parameters such as cutterhead aperture ratio, tool combination height difference, and cutter spacing on shield tunneling efficiency and formation deformation by PFC3D and field test. The results show that the driving speed under the spoke-type cutterhead is better than that under the panel-type cutterhead for the same tunneling parameters, while surface deformation and disturbance range to the surrounding strata are less under the panel-type cutterhead with the small cutterhead aperture ratio; When the height difference between the ripper and the scraper is 70 mm, the shield tunneling efficiency is higher and the cutterhead torque is lower; when the ripper spacing is 300 mm, the shield tunneling efficiency is better and the cutterhead torque is lower. Engineering practice shows that the spoke-type cutterhead with large aperture ratio and multidimensional configuration method for cutting tools are the foundation to realize the long-distance shield driving, and the tunneling parameter control with high penetration and low speed is the key. The results of this study provide a theoretical reference for cutterhead selection and tool arrangement in shield construction under similar projects.

Key words: Beijing new airport line tunneling project, sand-pebble stratum, PFC3D, cutterhead aperture ratio, height difference of tool combination, ripper spacing