Stirling Interchange Drainage Upgrade

Background

The Stirling Interchange is located on the South Eastern Freeway in South Australia, approximately 16 km from Adelaide’s CBD. The Freeway is critical to South Australia’s economy, as it forms the major road access to the eastern and southern areas of South Australia and to Victoria. It is the major route for interstate freight movements delivering up to 27,000 tonnes per day, representing around 48% of the State’s daily interstate goods transport.

The Stirling drainage culvert comprised 442 m of twin 1500 mm diameter corrugated steel drainage pipes following the original creek alignment up to 11 metres under the Stirling Interchange. In 1984, a 6 m deep section of the culvert collapsed, causing the partial collapse of the roadway and edge of the South Eastern Freeway. Despite repairs, ongoing deterioration of the steel pipes raised ongoing concerns about safety.

Key features

  • Resleeving of the exiting culverts—two options were considered for the deteriorated twin 1500 mm pipes. The first was the traditional method of replacing the culvert with new reinforced concrete pipes on a new alignment. This would have caused major disruption to the busy South Eastern Freeway traffic and considerable angst and economic loss.

    The preferred option was the structural resleeving of the existing steel pipes, with minimum 1050 mm diameter reinforced concrete pipes. The above-ground works were contained within the interchange and the resleeving option eliminated extensive excavation. This approach was effective in delivering the project with no disruption to the free flow of traffic on the freeway, and minimal disruption and delays on the access ramps.
  • Motorised remote controlled pipe trolley—the key to the construction was the innovative design of a motorised pipe trolley to drive inside a 1050 mm concrete pipe. The trolley was operated from the surface by remote control. It had three sets of hydraulics to lift the new 1050 mm pipe, transport it within the existing culvert and place it into position. CCTV cameras enabled personnel to monitor the works remotely, without the need to enter the confined space.
  • Ancillary structures—a concrete jacking chamber was designed and constructed one third of the way along the existing culvert. This enabled pipe sections to be lowered to invert level and installed using the motorised trolley. Other ancillary structures included the upgraded inlet and outlet structures, including scour protection, to ensure the 100 year design life was achieved.
  • Environmental management—regular monitoring of water quality demonstrated significant reductions in turbidity during and following the project. A natural spring located near the works was not disrupted. Site works were closely managed to contain any spread of Phytophthora and weeds. The project significantly improved the amenity of the whole site.
  • Safety—working in a confined space in the third wettest summer on record had the potential for disaster. However, innovative technology and Leed’s highly developed safety systems were combined to deliver a safe workplace. In particular, the pipe trolley contributed significantly to the safety of the confined space operations.

Outcomes

The Stirling Interchange Drainage Upgrade project was a resounding success due to innovative design, sound engineering practices and the collaborative partnering approach between DPTI and Leed.

The upgrade was completed ahead of time and under budget without impacting the major trade route into and out of Adelaide, despite the third wettest summer on record. Use of an innovative motorised pipe trolley was the key to the safe and efficient installation of new pipes inside the existing culvert under the South Eastern Freeway.

Awards

South Australian Engineering Excellence Awards 2011: Commendation for Project Infrastructure (together with Department for Transport, Energy and Infrastructure)

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