Rail link tunnel bore starts this

The first Robbins tunnel boring machine (TBM) will start work this month on the twin tunnel 13km Chatswood to Epping rail link in north Sydney.

They are expected to travel at between 120 and 180m a week in gouging 7m diameter twin tunnels mostly through Hawkesbury sandstone. They will start from what is known as the M2 site in Macquarie Park, about halfway between Chatswood and Epping. Once they reach Epping they will be brought back to M2 to relaunch towards Chatswood. In a best case scenario, with both machines starting at the same time, the job would take about 18 months. But it is expected to take until late 2005, providing leeway of eight or nine months for all eventualities.

A conveyor will be used to extract soil and rock from the work face and carry it back to the tunnel starting point at Chatswood.

Hunter built

The TBMs had previously been assembled, tested and then disassembled near Newcastle in the Hunter region north of Sydney.

Their manufacture had been underway since January, bringing around 70 direct jobs and more than $13 million to the local economy. More than 100 companies from the Hunter have been involved in helping build, assemble and test the 210m long, 1000t TBMs which are worth about $50 million combined.

The cutterhead (pictured) was one of 40 early morning deliveries from Newcastle for the two TBMs. Upon arrival to the worksite each section was lowered down a purpose built access shaft measuring 20 x 25 metres wide and 30 metres deep.

The Thiess Hochtief joint venture is responsible for the design and construction of the twin 12.5 km tunnels, together with the installation of rail track and information systems between Chatswood and Epping.

The joint venture also began excavating the Macquarie University station cavern in July and site establishment of the Delhi Road station started mid winter.

Cut and cover

A cut and cover tunnel will be constructed under Lane Cove River using de-watered cofferdams, which will cross the river in two stages. The first coffer dam is in place on the eastern side of the river and the first section of the cut and cover tunnel is being excavated. The roofs of the tunnels will be 1m below the riverbed.

Construction of the cut and cover tunnel started earlier this year following the establishment of the worksite. It is due for completion in early 2005.

The laying of rail track and installation of signalling and other communications systems between Chatswood and Epping will start in early 2006. This will continue until late 2007, after which the new rail line will be tested for operational efficiency and safety.

Dive structures and integration works

Dive structures will be built at locations where the underground tunnels meet the surface tracks. Integration works will connect the new rail link with the existing Main North Line at Epping and North Shore Line at Chatswood. These works will include the rebuilding and/or upgrading of a number of road and rail bridges and associated infrastructure along the Chatswood rail corridor. Integration works will continue in stages until late 2006.