CLIENT

Baulderstone Hornibrook & Bilfinger Berger

PROJECT

The Cross City Tunnel

PROJECT DESCRIPTION

Tunnel joint venture constructors asked Combined Saw Cutting to scope and execute the removal phase of the project

PROJECT DURATION

March 2004

PROJECT VALUE

$ 1.5 million

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BACKGROUND

As part of the Cross City Tunnel project, which links the Eastern and Western suburbs of Sydney, the feeder road from Sir John Young Crescent to the Cahill Expressway and Sydney Harbour Tunnel required widening.

This involved extensive modification to the abutment of the Art Gallery Road bridge.

The project was carried out in 3 stages:

• Digging out behind the existing abutment to construct a new abutment;
• Transferring the weight of the bridge from the original to the new abutment; and
• Removing the original abutment.

KEY CHALLENGES

As the work was being carried out within 1m of the road, the carriageway had to be closed and that was only possible between 10.00pm and 5.00am.

The abutment consisted of five columns each 5.3m high by 600mm thick and between 1.4m and 1.2m wide.

Between each column was a 200mm thick curtain wall.

The weight of each column was about 10.3 tonnes with the weight of each section of curtain wall about 5.3 tonnes, making a total weight of almost 73 tonnes of concrete to be removed.

PROJECT METHODOLOGY

The first stage involved core drilling and wire sawing to cut and remove the columns in 1 tonne sections.

Each column was divided into four pieces, the top pieces weighing just less than 1 tonne, and the bottom piece around 3 tonnes.

The second stage involved core drilling and pre-cutting to allow lifting chains to be put in place prior to making the final cut to free the 2 tonne section of wall for removal.

PROJECT SUCCESSES

The work was safely and effectively carried out within 1m of the carriageway, within the allocated time and without any damage to the public environment.