A total of 7 roadheaders were used in construction of Town Hall Station and State Library Station.
Our roadheaders worked together deep underground to mine the CBD station caverns.
In line with tradition, the roadheaders were named after women, which is thought to bring good luck to a tunnelling project.
Roadheaders are large excavating machines fitted with a mounted cutting head. They were essential in building the trinocular design of our 2 underground CBD stations.
This unique design combines 3 overlapping tunnels which integrate the concourse and platforms on a single level to create a wide, central tunnel space, for improved passenger circulation and vertical transportation.
This construction technique is uniquely suited to the CBD's highly variable geological conditions.
Our roadheader fleet carved out the space for the 19m-wide platforms at each station, advancing approximately 2m each day.
Once excavated, the caverns were reinforced with sprayed concrete, rock bolts and a final concrete lining.
Digging the station caverns
The roadheaders were lowered up to 30m underground in pieces, then re-assembled for digging. Each roadheader weighed 118t, was 15m long and could smash through rock 3 times harder than concrete. They dug an estimated 1500t of rock for the Town Hall and State Library station caverns combined.