10. Conclusion

Although tunnel boring machines (TBMs) are now widely used to build underground structures, the machines are still being improved to make them more reliable and efficient.

The number of companies now using this technology is greater than it was twenty years ago, but this should not lead us to believe that these machines can be used without solid experience. While some geologies are tolerant of variations in containment pressure, more often than not, inadvertent deviations from set values can have catastrophic consequences for both the project and the environment.

Experience in operating and maintaining machines efficiently is a skill that takes time to acquire.