Sydney Harbour Tunnel
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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 900metre land tunnels on the north shore, twin 400-metre land tunnels on the south shore and a 960-metre immersed tube (IMT) structure.
The IMT structure consists of eight precast concrete units. The units were constructed over 100 kilometres 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 earthquakes and sinking ships. It carries around 75,000 vehicles a day.
The Harbour Tunnel was a joint partnership between the NSW State Government and private investors via tender. Transfield International constructed the tunnel under contract . The tunnel is currently on a thirty-year lease, and will be handed back to the NSW State Government in August 2022. The tunnel was opened to the public to walk through from North Sydney (Falcon Street) to South Sydney (The Domain), on August 27 1992. The proceeds of the tickets sold for this event were donated to the Royal Deaf and Blind Society of NSW.
There was a lot of skepticism surrounding the appointment of Transfield International to build the tunnel, after other projects including IMT tunnels, carried out by the group, developed structural problems resulting in leaks.
One of the the northern end pylons of the Sydney Harbour Bridge was altered to allow for air exhaust from the tunnel to rise over the harbour. Bradfield Park on the northern side of the bridge also has hidden air intakes behind some conspicuously placed bushes.
Operations
The tunnel has two lanes in each direction. The tunnel runs at an angle of approximately thirty degrees (North to South) to the Sydney Harbour Bridge, which has eight lanes, variable in direction. Only southbound traffic (for both tunnel and bridge) attracts a toll.
References
- Pratley, Juliet (1993) "Sydney Harbour Tunnel", Concrete International 15 (7) 19-23.
- Franulovich, Adrian (1992) "The Sydney Harbour Tunnel Project".