Australian construction joint venture Transfield Obayashi is facing the threat of legal action from Transurban City Link after being blamed for leaks in Melbourne’s A$500M (US$256M) Burnley Tunnel. The tunnel was closed on February 19, barely two months after it opened on December 28, 12 months late. It was partially reopened a week later after costing Transurban A$700,000 (US$357,000) in lost revenue.
Kim Edwards, Transurban City Link managing director, indicated that Transurban could sue Transfield Obayashi for damages after an engineering report confirmed that a joint failure caused the tunnel’s wall to crack causing ingress of water. He said, "Transfield-Obayashi JV has been paid $500M to deliver a tunnel to last 120 years and is responsible under the contract for any defects".
The cross-section of the tunnel consists of a substantial flat invert slab joined to curved sidewalls, and the local failure involved primary and secondary cracking in a section of the south sidewall. A roughly semi-circular panel of the sidewall had rotated with the toe of the arch sidewall where it contacts the invert slab, moving towards the tunnel centreline by about 30mm.
The inside face of the hinge line shows aspects of the concrete crushing and pre-existing tension cracks coalescing. The traffic barrier close to the sidewall moved inwards by a maximum of about 50mm.
As a result of the movement the membrane built into the structure ruptured locally and water leaked into the tunnel. It was reported that this leak was of the order of 5 litre/s, which compares to the figure of 100 litre/s during the problems with the invert prior to the opening of the tunnel. The rupture of the tunnel membrane led to a rapid reduction of the loading on the arch. In this incident there was no movement of the tunnel invert itself and the structural mechanism appears to involve the joint between the sidewall and the invert slab.
A 1.5km stretch of the 4km long tunnel will remain partially closed until at least May while repairs are made. The damaged section of tunnel wall was due to be removed by March 23, ready for repairs to begin by April 1. Work is expected to take six weeks to complete.
In the meantime, the Melbourne City Link Authority has asked Transurban to compensate motorists for the delays while repairs are carried out. Possible options include crediting motorists’ toll accounts or making the tunnel toll-free at weekends.
