Comparison Study on the Rock Cutting Characteristics of Disc Cutter under Free-face-assisted and Conventional Cutting Methods

To improve the excavation efficiency of Tunnel Boring Machines (TBMs), the free-face-assisted rock cutting method induced by TBM disc cutter (FM) was explored and the differences between the FM and the conventional Cutting Method (CM) were also compared based on a series of rock cutting tests. The results show that when the free face distance is less than a critical value, the FM can promote the tensile failure of the rock and the formation of big rock debris effectively. Moreover, the cutting efficiency and the cutting forces including normal force, rolling force and side force of the disc cutter under the FM are also significantly reduced and improved, respectively, compared to that under the CM. The FM can be applied in multi-stage cutterhead TBMs to improve the cutting efficiency and reduce the failure of the disc cutter, the research results indicate that the free face distance should be controlled within 80 mm to use the free face effectively.