Rock-Breaking Mechanism of Disc Cutters and Rock Muck Characteristics for the Conical Cutterhead of Shaft Blind Full-Face Boring Machine

To investigate the rock-breaking mechanism of disc cutters at the conical surface of conical cutterhead, a three-dimensional model of rock fragmentation by disc cutters was established using the discrete element method. The study analyzed the influence of five factors on crack propagation and rock muck characteristics: the oblique angle of conical cutterhead, the installation inclination angle, cutter spacing, penetration of disc cutter, and the in-situ stress. An orthogonal experimental design was employed to determine the significance of each factor. The results indicate that rock cracks propagate obliquely downward. The cutter spacing, installation inclination angle and oblique angle have the significant impact on the average particle size of rock muck. As the installation inclination angle decreases, the rock failure morphology transitions from inclined shape to stepped shape, and the optimal cutter spacing increases. For moderately weathered granodiorite with oblique angle of 40°, the optimal parameter combination is a 30° installation inclination angle, 85 mm cutter spacing, 10.0 mm penetration, and 1 MPa in-situ stress, thus the average particle size of resulted rock muck is larger. These findings provide reference for optimizing the installation layout of disc cutters on conical cutterhead used in Shaft Blind Full-Face Boring Machine.