A tunnel boring machine excavates a full-diameter tunnel with a rotating cutterhead while supporting the ground behind it. TBM work is used for larger-diameter utility tunnels and long crossings where a casing or carrier pipe needs more room than a bore can provide.
How TBM Excavation Works
- Launch shaft. The TBM is lowered into a launch shaft and set on line and grade.
- Excavation. The cutterhead advances through the ground while the machine shield supports the opening.
- Lining or casing. Tunnel liner plate or casing pipe is installed behind the machine as it moves forward.
- Carrier installation. The utility line is installed inside the finished tunnel.
When TBM Excavation Is the Right Call
- Larger-diameter crossings beyond typical bore sizes
- Mixed or difficult ground conditions
- Crossings that need room for multiple carrier lines
Why Owners Specify It
- Size. Builds openings larger than other trenchless methods.
- Ground support. The shield protects the excavation as it advances.
- Long service life. A lined tunnel protects the lines inside it for decades.
Planning a large-diameter crossing?
To confirm or correct
Review draft only. This box will be removed before launch. Please reply with corrections to anything on this page.
- Do you perform TBM work, or partner with a firm that does?
- TBM sizes and diameter range
- Lining methods used (liner plate, steel casing)