Periodic inspection of gauge cutter wear on EPB TBMs using cone penetration testing

• A new test for measuring the length of gauge cutters in EPB TBMs is introduced.
• The procedure for performing the test has been summarized.
• The initial results related to this testing device have been reported.
• The results showed that the length of gauge cutters can be measured by measuring the length of the overcut.

Cutterhead maintenance is usually required when the gauge cutters (over-cutters) wear down to the shield diameter. In soft ground pressurized shielded TBMs, inspection of gauge cutters usually involves complete stoppage of the operation. This can be a dangerous, costly, and time consuming process. In this study, a novel approach has been developed to monitor gauge cutter wear by considering the relationship between the overcut length and the length of the gauge cutters. By using the proposed testing system, frequent monitoring of gauge cutter length is possible at appropriate intervals during ring builds or maintenance without the need to enter the harsh environment of the excavation chamber. This monitoring system was used within an EPB TBM during the excavation of the University Link Light Rail Tunnel (U230) in Seattle, WA.