Double Shield TBMs in Hard Rock: 19-Inch Cutters, Segment Lining, Faster Advance

In hard rock, the difference between a good and a mediocre advance rate usually comes down to how much of the shift is spent actually boring. A Double Shield TBM uses its grippers to thrust against the borehole walls while a segment ring is erected under the protection of the rear shield, so excavation and lining proceed in parallel. Single-shield machines must stop to build each ring, and that downtime compounds over kilometres of tunnel. The cutting side matters just as much. Nineteen-inch heavy-duty disc cutters carry higher thrust loads and run at greater penetration per revolution than smaller discs, which reduces the number of passes and the frequency of cutter changes in abrasive, high-strength rock. Wear reduction comes from the whole system: robust cutterhead design, hardfacing on the face, controlled muck flow and systematic cutter-wear monitoring rather than reacting to failures underground. The productivity gain is matched by a safety gain — crews erect segments inside the shield, and ground support follows the machine closely. For long mountain drives, that combination is hard to beat. It also suits transitional ground, where desert metros and road tunnels in the Middle East often hit sand-and-rock mixed faces. OUSUN, based in Deyang, Sichuan, supplies 19-inch cutters, seals, segment bolts and screw conveyor parts with roughly 2–4 week lead times; [email protected].