Influence of Rock Joints on Rock-Breaking Efficiency of TBM with a Double-Edge Disc Cutter

The structural planes of rock masses have a significant influence on the rock-breaking efficiency of the Tunnel Boring Machine cutter. The particle flow program, incorporating the linear parallel bond contact model, is adopted to investigate the micro responses during the invasion process of the cutter. The impact of the joint characteristics, including the number, dip angle, spacing, and cross joints, on the rock-breaking efficiency, was investigated in this study. Moreover, the propagation path of microscopic cracks and the occurrence of fracture zone were analyzed. The results show that: (1) The direction and depth of crack propagation are controlled by the joint. Additionally, the microcrack tends to propagate along the direction of the joint, and a migration phenomenon is observed; (2) The generation of rock debris and rock blocks are primarily determined by tension cracks; (3) When the joint angle is small, the rock-breaking efficiency is higher; (4) The difference in the number and spacing of joints leads to the difference of the crack density. When both of them take the median value, the rock-breaking efficiency is highest; (5) As the angle of the cross joint increases, cracks can propagate to the deep part with the range of the fracture zone expanded, resulting in the improvement of the rock-breaking efficiency.