Almost a year after the Tunnel Boring Machines (TBMs) were installed, the twin Metro tunnels on the Beauty World Project have now been completed. As the final pieces of the 1000 tonne boring machines are being dismantled and demobilised from site, it is a good time to reflect on our achievements.
The range of geological conditions that these 6640mm diameter ‘monsters’ bored through was as impressive as it was challenging. The geology ranged from unweathered 200 MPa granites to completely disintegrated soils, including the hardest soil conditions of them all, ‘Mixed Face’. This involved boring through hardrock and clay at the same time. The tunnelling teams and crews performed admirably in the trying conditions with almost all interventions (for TBM maintenance) performed under compressed air entry.
Despite these challenges, the advance rates for the TBMs were impressive, particularly in the later stages of operations. Importantly, the McConnell Dowell team at Beauty World is the first contractor on the DTL2 scheme to complete their tunnelling operations. We have completed all our tunnelling operations on program and Lost Time Injury Free.
We are now moving ahead with the technically challenging Cross Passages that link the twin tunnels, and completing the remainder of the underground Beauty World Station beneath the live traffic of Bukit Timah Road.