Sydney Harbour Tunnel - Definition and Overview

The Sydney Harbour Tunnel is a tunnel in Sydney, Australia. It was completed in August 1992 to provide a second vehicular crossing of Sydney Harbour to alleviate congestion on the Sydney Harbour Bridge. The tunnel is made up of three sections: twin 900 m land tunnels on the north shore, twin 400 m land tunnels on the south shore and a 960 m immersed tube (IMT) structure.

The IMT structure consists of eight precast concrete units. The units were constructed over 100 km away in a dry dock at Port Kembla and then towed to Sydney Harbour. A trench was dredged prior to the arrival of the IMTs and then the IMTs were lowered into the trench by a system of pontoons and control towers. After the IMTs were in place the trenches were backfilled and then a rock armour was placed over the top to protect the units against marine hazards, such as anchors or sinking vessels.

The land tunnels were constructed by a combination of driving and cut-and-cover techniques. The total construction cost of the project was A$554 million. It was designed to be strong enough to withstand the impact of eathquakes and sinking ships. It carries around 75,000 vehicles a day.

References

• Pratley, Juliet (1993) "Sydney Harbour Tunnel", Concrete International 15 (7) 19-23.

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