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The construction of the Epping-Chatswood rail line is the largest public-private funded infrastructure project in New South Wales, providing a much-needed cross-link in Sydney’s urban transport infrastructure. Chatswood, on Sydney’s North Shore, will be a major interchange for the new railway line. It has had a railway station since 1890 and is currently the ninth busiest station on the City Rail network, used by some 35,000 rail commuters daily – anticipated to increase to 100,000 commuters by 2021 with the opening of the new Epping link.

The Chatswood Transport Interchange (CTI) is being developed as a Public Private Partnership with Laing O’Rourke (BMC) Pty Limited as the design and construct contractor. This multi-faceted engineering and building project involves the design and construction of both a temporary and a new railway station comprising twin island platforms and commuter concourse, bridgeworks, new bus interchange, taxi ranks, kiss-and-ride facilities, basement car park, 10,000 m2 of convenience-based retail, and rail track work to accommodate the new Epping to Chatswood line. The project also includes provision for the future construction of three residential towers over the interchange.

“The main issues for the design team were isolating the vibration caused by the trains and separating this vibration from the residential towers (to be built in the final stage) – and that’s where we’ve used the Trelleborg floating slab bearings, to prevent any reverberation traveling through adjoining structures,” says Laing O’Rourke project engineer Chris Paras. He explains one of the major project challenges: “For the private development partner, the key component was the three towers and the shopping centre while for the public partner, the key requirement was to keep the train station open and the trains running during construction. As the basement car park had to be built underneath the existing station, we had to move the station while we built half the basement and then move it back to complete the rest,” says Paras.

Paras says this is the first time floating slab bearings have been used in heavy rail in Australia. He and his team had previously used isolation base plates (called Cologne Eggs) on fixed track slab at Bondi Junction train station, but the floating slab track created a new challenge. Finding the best way to isolate the main slab – which supports the track, station, shopping centre and the three towers – was imperative. “Trelleborg bearings have a good reputation in the rail industry generally and had some history with Railcorp, the NSW railways operator,” says Paras.

The Trelleborg product has demonstrated that it met their stringent requirements, including a life expectancy of 50 years. The Laing O’Rourke team travelled to Hong Kong to see the Trelleborg bearing pads in a similar railway application and then based their needs on the product’s performance in Hong Kong. “The main Trelleborg bearings were bonded on the underside of the pre-cast slab sections and the lateral bearings then had to be inserted on the long side. Side bearings had to be compressed for installation and the tolerances were only plus or minus one millimeter either side,” says Paras.

“We came up with a system that made it relatively easy to install them despite the tight tolerances. Our rail crews saw this as a good opportunity to learn some new skills and didn’t baulk at the challenge. Although the first 400 meters floating slab track they installed took two weeks, the second one took only a week.”

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Floating Slab Track (FST) Bearings

Floating Slab Tracks (FSTs) are a proven mass-spring system for achieving very high levels of vibration isolation. FST bearings are suitable for reducing low-frequency ground-borne vibrations. The rail track floats on this rubber bearing system. They are used in close proximity to noise-sensitive structures such as performance halls, residences, schools and office buildings.

Trelleborg Queensland Rubber, a unit within Trelleborg Engineered Systems, designed and manufactured acoustic vibration isolation bearings for the Philadelphia Theatre Company in the United States and thousands have been supplied for the east and west rail extensions in Hong Kong.

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