Hard Rock Tunnel Boring at Nye Ulriken Tunnel - Rock Breaking and TBM Performance

Abstract

This report is based on a conducted field study at the Nye Ulriken tunnel project. The main goal was to better understand the interaction between TBM and rock face in hard rock formations in general and for Nye Ulriken tunnel in particular. The goal was achieved by:

Performing detailed geological mapping Collecting rock samples to be analysed in the laboratory and in the field Collecting TBM performance data Investigating the reliability and accuracy of the NTNU prediction model

TBM performance data are showing some variation in the initial phase. There is a possibility to increase total advance force to some extent if allowed by geological conditions and if not affecting cutter life in a negative way. For RPM, the limited results from the penetration tests indicates that average RPM until now has been decent for the average thrust applied. The interpretation of the geology prior to the project had room for improvement, so the possibility of doing more testing and mapping from the existing tunnel could have been more exploited. The fracturing factor in the NTNU model correlates with the actual penetration rate of the project, but the mapped fracturing resulted in a low estimated penetration rate. The model seems to be sensitive to the subjectivity of fracture mapping.