How fast can a tunnel boring machine drill?The drilling speed of a Tunnel Boring Machine (TBM) varies significantly depending on factors like the type of TBM, ground conditions, tunnel diameter, and the overall project requirements. Generally, the speed can range from 10 meters to 50 meters per day under typical conditions.
Factors Influencing TBM Speed:
1. Type of TBM:
- Earth Pressure Balance (EPB) TBMs: Commonly used in soft ground and can achieve speeds of 10-20 meters per day.
- Slurry TBMs: Used in unstable ground with high water pressure, typically achieving speeds similar to EPB TBMs.
- Hard Rock TBMs: Used in solid rock, where speeds can vary from 5 to 20 meters per day depending on rock hardness.
- Double Shield TBMs: Can be faster, drilling up to 50 meters per day in favorable conditions.
2. Ground Conditions:
- Soft Soil: Easier to drill, often allowing for higher speeds.
- Hard Rock: Slower due to increased resistance and the need for more powerful cutting tools.
- Mixed Ground: Challenging and often slows down the TBM due to the varying material types.
3. Tunnel Diameter: Larger diameters typically slow down the TBM, as more material must be excavated.
4. Operational Factors: Maintenance, logistics, and the efficiency of muck removal can also impact the overall drilling speed.
These speeds are averages, and actual project conditions may result in faster or slower progress.
Some of the fastest recorded speeds for TBMs include the “Bertha” TBM used in the Alaskan Way Viaduct Replacement Project in Seattle, which achieved an average speed of about 15 meters per day, despite encountering unexpected obstacles. In China, TBMs have been known to achieve speeds of up to 100 meters per day in optimal conditions.
