The Highway
The Kwinana Freeway extension and Forrest Highway extends the dual carriageway 70.5 kilometres from the existing Kwinana Freeway at Safety Bay Road in Baldivis to Old Coast Road in Lake Clifton.
The Kwinana Freeway extension comprises 32 kilometres of freeway standard road from Safety Bay Road in Baldivis to South Yunderup Road, South Yunderup. The remainder of the route, the Forrest Highway, is a rural highway with the ability to be upgraded in the future as traffic demands increase. The entire route is continuous dual carriageway, with two lanes in either direction.
Six grade-separated interchanges are provided on the Kwinana Freeway extension at Safety Bay Road, Karnup Road, Paganoni Road, Lymon Road, Lakes Road and Pinjarra Road. With the exception of the Pinjarra Road interchange, these were constructed as diamond interchanges, allowing for movements in all directions. The Pinjarra Road interchange was constructed as a Parclo interchange, where all the on and off ramps are provided on the northern side due to the proximity of the Murray River.
Ten intersections are provided on the Forrest Highway and have the capacity to be upgraded to interchanges in the future. They are located at Beacham Road, Greenlands Road, Paull Road, Mills Road, Birchmont Road, Herron Point Road, Old Bunbury Road, Dorsett Road, Old Coast Road and Peppermint Grove Road.
Pavement Design - Kwinana Freeway extension
Approximately 8 million tonnes of sand and limestone, which was sourced from various borrow pits near the alignment, was brought into the site and provided the 250mm foundation for the road surface.
Approximately half of the freeway surface comprises a crushed rock layer with an asphalt seal, which provides mitigation of noise emitted from freeway traffic.
The remainder, the northernmost 15 kilometres of the freeway, was constructed using thick-lift asphalt, which possesses the same noise reduction quality, but also provides a more durable surface for the section with the highest traffic volumes.
The thick-lift section consists of five layers of asphalt – one basecourse layer, two intermediate layers, one dense grade asphalt layer and finally an open grade asphalt layer – which were placed one stratum at a time by an asphalt paver.
The majority of the asphalt produced for the Kwinana Freeway extension and ancillary works was manufactured at the temporary batching plant at the project’s Baldivis site. Approximately 200,000 tonnes of asphalt was used to construct the freeway.
To produce the asphalt, aggregate was fed into a rotating drum dryer/ heater in order to evaporate all moisture from the contents and heat the material. The hot aggregate was then added into a pugmill and mixed with hot bitumen to bind it together.
The resultant product, hot mix asphalt, was transferred to site and laid the same day, which is why the close proximity of the batching plant to the alignment was essential.
In the final months of the project there were up to six asphalt crews operating concurrently on the freeway and they managed to lay a combined average of 5,000 tonnes of asphalt per day.
Forrest Highway
The majority of the Forrest Highway travels through a floodplain and required the import of more than 5.5 million tonnes of sand and limestone to raise the road level above the areas of seasonal inundation.
This material was also sourced from various borrow pits near the alignment and provided the 250mm foundation for the road surface, which comprises approximately 300,000 tonnes of Crushed Rockbase (CRB).
The CRB is a manufactured basecourse pavement material produced from quarried hard rock, typically granites and dolerites of the Darling Scarp.
The blasted and crushed material is mixed with water in a pugmill and then stockpiled on-site – a unique opportunity for an Australian road project – which increased efficiency and improved accessibility for the paving operations.
The Alliance had three primary stockpile locations – Stake Hill, West Pinjarra and Lake Clifton – which could hold a combined 360,000 tonnes at any one time.
The first amount of CRB was placed on 13 August 2008 and approximately 6 months later, the highway paving was complete, with crews placing an average of 860 metres of road base per day.
The process was assisted by a German manufactured paving machine – the only one of its kind in Australia – which could pave the entire width of the carriageway or 11.7 metres in one pass.
The position and level of the paving machine was guided by GPS and worked in tandem with a transfer vehicle. Rollers then followed the paving machine to complete the full operation, before the road was finished with a bitumen seal.
Delivering Efficiency - Machine Guidance Technology
More than 14 million tonnes of material was required to construct the route and historically, a project of this size would have relied on a large team of surveyors to peg the alignment and guide construction activity on-site.
Southern Gateway Alliance however took advantage of wireless technology to rapidly transmit data between the field and the design office with just a few key strokes on a computer.
Haefeli-Lysnar, Trimble’s distributor in Western Australia, met the Alliance’s requirements with a unique combination of machine control systems and a wireless communications network that represented a world first in application of the technology.
The Trimble system allowed the Alliance to fast track construction and efficiently manage issues surrounding the highway’s evolving design.
The system virtually placed the site plan, design surface, grade and alignment, inside the cab of the earthmoving equipment. Using the GPS, the exact position and very accurate cross slope and heading of the blade or cutting edge was measured. The on-board computer then used this information and compared it to the design elevation to compute cut or fill to grade.
The value of the system was its ability to handle and view data in real time, increasing responsiveness and productivity.
On this project, SGA purchased and fit 30 Trimble machine control systems into earthmoving machines and supervisor’s vehicles.
World Class Paving Machines
To enhance the efficiency of the paving program, the Alliance used innovative machinery including German manufactured paving machines, Paveset machine guidance technology and Microlance instant moisture content devices.
The paving machines were the only two of their kind in Australia and could lay the entire width of the 11.7m carriageway in one pass.
Toward the end of paving operations, the crews averaged almost 900m of dual lane carriageway each day, almost double the earlier predicted amount.
One machine, with a crew of seven people, operated in each of the construction zones and was guided by GPS technology for line and level control without pegs.
Awards
Southern Gateway Alliance received various awards for the use of machine guidance in constructing the Kwinana Freeway extension and Forrest Highway. These are below:
2009 Asia Pacific Spatial Excellence Awards
- Construction and Infrastructure Award for Excellence
- Overall Award for Excellence
2009 Surveying and Spatial Science Institute of WA Awards
- Construction and Infrastructure Award for Excellence
- Overall Award for Excellence
Monitoring the highway - Intelligent Transport System
With more than 30,000 motorists expected to use the new route every day, traffic monitoring was an essential component of the road’s design.
An Intelligent Transport System was installed throughout the entire length of the 70.5km route, providing rapid, automatic incident and congestion detection, which will ensure proactive traffic management during an event
Monitored by Main Roads, the system also provides information to motorists on alternative route selection and journey planning information including current congestion data.
Unlike any other road project in the country, the ITS on this project was installed via a unique plowing method and blown fibre technology.
The plowing practice saw a trench excavated with a specially designed vibratory blade, pulled through the ground at a pre-set depth. Following this, the cable and pipe was laid with an automatic sanding hopper, which then filled the trench as the machine advanced.
The plowing machine had an onboard Global Positioning System (GPS), which displayed the proposed route line and mapped the depth and positioning of the pipe being laid.
In the next stage of the ITS installation, approximately 230 concrete pits were established, providing access points for the cable installation and blowing.
The mini fibre cable was placed into a preformed internally tubed duct and using a specialised air compressor, the cables were propelled through the tubes within the duct at a maximum of 2km per operation.
The services the ITS provides for the Kwinana Freeway extension and Forrest Highway include emergency telephones, CCTV cameras, vehicle detection systems and variable messaging signs, which all operate in conjunction with Main Roads’ Traffic Operation Centre.
An advanced warning system was installed at intersections on the Forrest Highway, which is unique to this type of system. This particular ITS is also upgradeable and lends itself for additional devices, if they are required in the future.
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