Spherical hobs are very mature and are widely used in many equipment, such as rotary drilling rigs, RCD, pipe jacking machines, etc. By analyzing the use of ball-tooth hobs on the above equipment, it can be known that when there is sufficient propulsion pressure and the rock layer strength is about 130MPa, the footage speed of the spherical tooth hob can be maintained at 0.3~0.5m/ h. And the footage speed is relatively stable. When the spoil discharge is sufficient, the service life of one spherical tooth hob can reach a construction length of 300m.
