In Australia, the first TBM broke through on 8 June on the final leg of its route for the 12.5km long twin tunnels on Sydney’s Epping-Chatswood rail link (T&TI, April, p10).

The Thiess Hochtief JV (THJV) was awarded the US$651M contract for civil and system works including the tunnel and station construction for the link in July 2002. The tunnelling works got underway just over a year later with the launch of THJV’s two 7.2m diameter Robbins hard rock TBMs, collectively valued at US$37M, from the M2 worksite at Macquarie Park.

By July 2004, the TBMs had completed their first stage of tunnelling from Macquarie Park to Epping. The machines were disassembled and returned to M2 for re-launch in November last year for the final 5.3km long leg in the opposite direction to Chatswood.

The breakthrough of the first TBM at Chatswood is a significant milestone for the project. Speaking at the breakthrough, Steve Burns, project director for THJV said: “This is a great day for the project and everyone involved in the works. This is the first time in Australia that two TBMs have worked side by side to create twin tunnels.”

The project also claims a new world record for the advance in 24 hours for a machine in the 7m-8m size category with an incredible 92m being excavated through Hawkesbury sandstone in one day on 8 April this year.

Commending the crews, Burns said: “The tunnelling works have been a very challenging and complex engineering task and the fact that we broke a world record along the way is reflective of the skill of the workforce and their level of dedication.”

The best weekly advance up to the time of the first TBM breakthrough was 368m in one week, with the daily excavation rate averaging 40m according to a document obtained from the project by T&TI.

Another equally impressive statistic is that of the 2.8Mt of sandstone spoil generated by the tunnels’ excavation, 100% is claimed to be reused, the bulk of it on the Western Sydney Orbital project.

When the second TBM breaks through, the tunnels will be substantially completed, although installations and fitting out remain ongoing. As T&TI went to press, the second TBM was expected to break through in early July.