The Cross City Tunnel
 As
part of the Cross City Tunnel project which links the
Eastern suburbs of Sydney to the Western, extensive
modification to the abutment of the Art Gallery Rd.
Bridge had to be undertaken to increase the width of
the feeder road from Sir John Young Crescent to the
Cahill Expressway/Harbour Tunnel.
The first part of the project was to dig out behind
the existing abutment and construct a new abutment.
The second stage was transferring the weight of the
bridge from the original to the new abutment and the
third stage was removing the original abutment.
ECR International was asked to scope the project by
the tunnel’s constructors Baulderstone Hornibrook
Bilfinger Berger Joint Venture. The abutment consisted
of five columns each 5.3 metres high by 600mm wide and
between 1.4 metres and 1.2 metres in width. Between
each column was a 200mm. thick curtain wall. The weight
of each column was about 10.3 tonnes and of each section
of curtain wall about 5.3 tonnes. In total there was
just under 73 tonnes of concrete to be removed. As the
work was being carried out within one metre of the carriageway,
the carriageway had to be closed and that was only possible
between 10.00pm and 5.00am.
The first stage of the project was to drill lifting
holes in the curtain wall, and then pre-cut the wall
using a wall saw. After the wall had been pre-cut, a
crane was bought and the crane’s chains were threaded
through the lifting holes. The final cut was made that
freed the section of wall being removed and the two
tonne section of wall was removed. This process was
repeated until all of the curtain wall had been removed.
The five columns were now exposed. Each column was divided
into four pieces, the top piece weighing just less than
one tonne, and the bottom piece weighing three tonnes.
The first stage of the process was for lifting holes
to be drilled. As we were using a wire saw to cut the
columns to size, wire holes, which are about 30mm. in
diameter, had to be drilled in the appropriate places.
We then cut all the horizontal lines. The columns were
held in position by the new abutment. A crane was then
bought in and hooked up to the top (one tonne) portion
of the column. This portion was then cut vertically
to separate it from the new abutment and then removed.
As there was very little head room, and there were some
tunnel services adjacent to the work area, removing
these top sections was difficult, but using an expert
crane company allowed the process to be completed without
incident. After the top pieces had been removed, it
was then a relatively easy task to remove the remaining
sections of column sequentially.
Click
here to download pdf detail sheet (pdf~312kb)
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