Sydney Metro CBD breakthrough

21 August 2019

Australia – The first TBM has broken through into the Pitt Street metro station in Sydney’s central business district (CBD). TBM ‘Nancy’, a double shield hard rock gripper machine manufactured by Herrenknecht has tunnelled 6km through sandstone and shale since launching from Marrickville in October. TBM ‘Mum Shirl’, excavating the parallel tunnel, is a few hundred metres behind.

The TBM will undergo maintenance before being re-launched towards by contractor John Holland CPB Ghella JV towards the Martin Place station then on to Barangaroo.

The project will see 15.5km of twin tunnels excavated in Sydney. It is the first time five TBMs have been in operation at the same time on an Australian infrastructure project. Four of the machines are 7.04m hard rock machines like Nancy, while one is a 7.01m Mixshield slurry machine that has been designed to tunnel under Sydney’s harbour.

The tunnel is being lined with a precast concrete segmental ring comprising six segments. Each ring has an external diameter of 6,690mm, an internal diameter of 6,170mm, a width of 1,700mm and a thickness of 260mm. Each ring is composed of four counter-key segments and two key segments.

The project should be delivered in 2024.