When a 90 years-old sewerage system serving Brisbane’s CBD, needed upgrading, the engineers were faced with a dilemma.
The problem was that the existing main in Coronation Drive was not big enough to handle diverted flows from the Heroes Avenue pump station.
However, open cut excavation to replace it was not an option, because no one wanted a repeat of the massive traffic disruption caused by earlier roadworks involving this major arterial road in a large city of Australia’s Sunshine State.
The solution implemented by McConnell Dowell Constructors was to lay a sewer rising main under Coronation Drive and link it to pipes in a new 1.2 metre diameter tunnel 650 metres long – 270m of which would run as a siphon beneath the Brisbane River from the West End bank to the Bi-centennial Cycleway opposite Park Road in Milton.
Commenced in 2004 and completed last year, the new line now connects with the S1 sewer tunnel that flows under gravity to a major pumping station at Eagle Farm, which in turn sends sewage to the Luggage Point treatment works.
A Herrenknecht AVN 1200 tunnel boring machine with a hard rock head drilled the cross-river tunnel between two 36 metre-deep shafts on either side of the river. A 1200mm internal diameter concrete pipe followed behind the TBM using hydraulic pipe-jacking techniques. When completed, four permanent pipeline strings were drawn through. The pipeline strings, one 450mm and one 300mm GRP and two 200mm PVC tubes, were assembled using 2.8 metre lengths.
According to McConnell Dowell Constructors, a set of four one-tonne Enerpac RC59 hydraulic jacks supplied by Blackwoods Coopers Plain was used to ram home the O ring-sealed joints in a high speed jointing operation that ran 24 hrs a day and took only two days to complete.
It was a good feat considering the complexities involved and the occasional need to modify the lengths on-site in the cramped water-tight chambers. Each of the four pipe clusters were lowered down the shaft on a fabricated trolley and joined to the main pipe string which was then drawn through the tunnel on the wheeled trolley system.
An Enerpac Turbo II air hydraulic pump, which uses its own exhaust gases to help boost pump power, was used to actuate the four RC59 cylinders (collectively giving 20 tonnes of force) through a four-way manifold governed by Enerpac manual V valves for safety and control.
Extending 200mm at a time (the length of the pipe joints) the rugged Enerpac system helped the engineers complete their jointing tasks within five 10-hour shifts over a single weekend. According to McConnell Dowell Constructors, everyone was amazed it went so well. Originally, McConnell Dowell had intended using a manual Enerpac jacking system, but quickly realised that a one-tonne powered Enerpac system would be far more efficient.
Once the liner pipes were installed and hydrostatic pressure tests completed, the void between the outside of the liner pipe and inside of the jacking pipe, within the 270-metre tunnel was filled with grout using 244 cubic metres of purpose-designed cement slurry.
The compact but strong hydraulic technology used in the pipe jointing component of the Brisbane project comes from one of the recognised global market leaders in high pressure (700 bar, 10,000psi) hydraulics, Enerpac, which manufactures an extensive range of hydraulic cylinders, pumps, rams, valves, presses, tools, bolting tools, accessories and system components for the manufacturing, mining, construction and engineering industries.
Enerpac’s technology, used in Australia and worldwide for more than 50 years, is employed on major engineering projects, on production lines and on maintenance, operation and repair equipment around the world.
Many demanding projects have been accomplished faster and more safely with Enerpac's integrated hydraulic systems and equipment. These range from tunnelling to the complex lifting of San Francisco’s Golden Gate Bridge to install improved earthquake-resistant towers and footings in an upgrade completed last year.
The Enerpac story dates back to 1910 at the beginning of industrialisation in the United States when the originator of the company made water pumps for the legendary Model T-Ford and other motor cars. Enerpac's reputation in the creative application of hydraulics started in the early 1920s when its first hydraulic jacks were introduced.
Now dedicated Enerpac teams are working around the world on designing and assembling reliable and efficient hydraulic systems for heavy construction, lifting, lowering, pushing, pulling, bending, holding, stressing, cutting, spreading and bolting.