Concrete makes it work - Sydney Metro Northwest  

Sydney Metro Northwest is revolutionising public transport in Australia and concrete is making it happen. The $8.3 billion project is a revolutionary computer operated driverless train public transport system connecting the North West of Sydney between Chatswood and Rouse Hill.

As a revolutionary transport system the trains will arrive at the stations every fifteen minutes (no need for a timetable) and stop within a millimetre of their mark with pre-marked door locations on the platform. 

The construction project consists of two major components: Twin Tunnels for fifteen kilometres and a four kilometre elevated bridge, called the Skytrain.  

The Skytrain is now making a spectacular appearance on the horizon at Rouse Hill as the concrete columns rise dramatically to support the double track superstructure. The bridge superstructure is constructed from precast concrete match-cast elements, manufactured by contractor Salini-Impregilo at a Mulgrave Precast yard. Each element is a full bridge cross-section and after elevation by crane it is held in its temporary position by a gantry. The group of bridge elements are then post-stressed into final position with stressing strand and the gantry advances on to the next span.  

The match-cast method wet casts one concrete unit against its neighbour in the precast yard to form a perfect fit. The units are manufactured under factory controlled conditions and brought to site when required. A total of 1,200 precast match-cast segmental units are being manufactured for the Skytrain.

Salini-Impregilo has installed two gantrys for bridge unit installation and together they are building seventy lineal metres of Skytrain each week. A blistering pace that is possible because of the use of concrete.     

A breath-taking cable stayed bridge will be constructed over Windsor Road (similar in appearance to the Anzac Bridge in Sydney Harbour) using the same cross-section, concrete units and casting method. A total of 80,000 m3 of premixed concrete is being used in the construction of the Skytrain.  

Concrete was selected as the Skytrain construction material after careful consideration of the visual impact of the structure on its environment. Competing materials could not provide the graceful curves, appealing form, and durable robustness required for this visually significant structure.

In addition, the unparalleled ability to manufacture bridge units quickly from concrete and to high precision was a critical aspect for the contractor; re-affirming that concrete is essential for the successful construction and completion of this project.   

The construction method minimises disruption to local road traffic allowing daily traffic volumes of 50,000 able to continue unhindered and without interruption. In addition, the completed Skytrain structure as an elevated line does not divide communities, but maintains the free flow and fluidity of local movement either side of the track, demonstrating that concrete is a construction material both of the people and for the people of the community.

On the next section of the Northwest Metro the tunnel segment is being constructed by the consortium of the Thiess John Holland Dragados Joint Venture and at fifteen kilometres in length are the longest railway tunnels ever to be attempted in Australia. The tunnels are being excavated simultaneously by four Tunnel Boring Machines. Two were launched from Bella Vista and excavate a circular cross sectional tunnel for a distance of nine kilometres to Cherrybrook; while at the same time another two Tunnel Boring Machines were launched from Cherrybrook and excavate a distance of six kilometres to Epping. Currently sixty per cent of the tunnelling is complete.  

Concrete provides the link that makes the bored tunnels work. As each boring machine advances, it places precast concrete tunnel lining segments in its rear position to shore and line the excavated rock. The lining segments are grouted into position providing the structural stability, soundness and waterproofing to the inside tunnel space – the public railway cannot operate without the surety that concrete provides. Automated computer operated driverless trains require a dependable, waterproof, stable tunnel configuration and it’s the concrete segmental tunnel lining that makes the rail tunnels work and it’s concrete that delivers this in style. 

The tunnel lining segments require around 150,000 m3 concrete and with another 100,000 m3 for structural work, bringing the total for the tunnel contract to 250,000 m3. All told, the Sydney Metro Northwest Project generates a requirement of 330,000 m3 of concrete.

The Sydney Metro Northwest is only the beginning; the NSW Government has announced that Stage Two of the Sydney Metro will extend the line from Chatswood, under Sydney Harbour through the Sydney Central Business District and south west to Bankstown. This transport system will place Sydney on par with the transport systems of Rome, New York and London. Sydney will be at the forefront of public transport in the world.   

Sydney Metro Northwest is a game changer for public transport in Australia, and concrete is the game changing material that makes it happen.  Concrete provides the missing link to make the tunnels work and concrete provides the construction method to make the Skytrain work. Concrete is the material of choice for the Sydney Metro Northwest delivering a durable, sustainable and resilient public transport system, which will ensure Sydney’s reputation as a global city.