TBM Disc Cutter

TBM disc cutter is pressed on the rock surface to be broken by the hydraulic system of the machine. In the process of working, the disc cutter rotates around its own axis, and at the same time it revolves around the central axis of the cutter head as the cutter head rotates. Under the combined action of the rotating torque of the cutter head and the vertical thrust of the propulsion cylinder, the disc cutters distributed on the cutter head cut out a group of concentric circles on the tunnel face. When the compressive strength of the rock is lower than the thrust of the cutter head, the rock will be directly broken by the cutter blade, thus forming multiple concentric grooves. With the advance of the cutter head, the groove depth gradually deepens, and the blade penetrates into the rock, forming crushing zones and radial cracks. Under further pressure, when the hob spacing meets certain conditions, the surface crack of the adjacent rock mass expands gradually, and finally the rock between the adjacent concentric grooves collapses, and the rock breaking process of the disc cutters is completed.

In the case of normal wear, we recommend that the disc cutter needs to be replaced when the cutter ring of gauge cutter is worn out about 10-15mm, and the cutter ring of face cutter and center cutter is worn out about 20-25mm. At this time, the cutting edge of the cutter ring becomes wider and its ability to cut rocks is reduced. The torque and thrust required for TBM tunneling will increase, which increases the load of the TBM hydraulic system and motor system, and the crushed rock will also wear the cutter head, thereby reducing the service life of the TBM.

The tunnel boring machine working principle relies on TBM disc cutters applying three forces: normal thrust to press into the rock, tangential force to shear it, and a minor lateral force. These forces induce extrusion, shear, and tensile cracking, producing muck tailored to rock properties and cutter design.

Choosing the right TBM disc cutter depends mainly on the tunnel's geological conditions. For hard, intact rock (e.g., granite with UCS >100 MPa), use single disc cutters or heavy-duty roller cutters with large diameter (19–20 inches) and high-wear-resistant rings to handle high thrust and abrasivity. In mixed ground or soft-hard transition zones, twin or triple disc cutters are recommended for better stability, chip formation, and reduced vibration. For soft or highly abrasive formations (e.g., sandstone, clay), prioritize cutters with advanced sealing systems and consider adding scraper tools. Key factors include UCS, CAI (Cerchar Abrasivity Index), quartz content, and groundwater.

The typical lifespan of a TBM disc cutter varies widely based on geology, operating parameters, and maintenance. In hard, abrasive rock (UCS 100–200 MPa), face cutters usually last 200–600 m³, while gauge cutters have shorter life due to higher peripheral speed, with wear rates around 0.2–0.5 mm per meter. In moderate or mixed ground, optimized conditions can extend life to 800–1500 m³ or more. Cutters are generally replaced when face/center rings wear 20–25 mm or gauge rings 10–15 mm.