Work on the $342 million Nowra bridge project continues to power ahead at an astonishing rate, with 38 of 39 piles required for the eventual 360 metre long bridge now driven into the river bed.
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The final pylon will be put in place in the coming weeks, weather permitting.
Thousands of us drive past the worksite each day and have marveled at the ongoing work - how the work site changes virtually daily as more and more pieces of the bridge puzzle are put into place.
We've seen the clearing of the site, the installation of a temporary rock platform into the Shoalhaven River with around 22,000 tonnes of materials, which will be removed once construction is complete.
We have seen the piling work undertaken on the rock platform and progress out into the river with work being undertaken on specially designed barges.
We have seen pylons being put in place and segments of the deck also moved.
So we asked Transport for NSW a few questions on how all the work is done.
Q: How are the piles constructed?
A: Once driven into place the project team excavates the material and pours concrete for the piles, which range from 23 metres up to 54 metres in length, dependent on the level of the rock foundation.
Q: How much concrete is in each pile?
A: Each pile is 1.5 metres in diameter and has concrete infill reinforcement up to 25 metres long, which requires around 44 cubic metres of concrete. Only the top section is required to be filled with concrete as the steel tube at the foot of the longer piles are strong enough to transfer the loads further down to the bedrock, but the shortest piles in the first pier at the north end of the bridge are full of concrete.
Q: We saw on the rock shelf area, excavations where footings for the pylons were constructed - how does that work the footings need to be constructed in the water?
A: Pre-cast pile cap tubs are built on land and then lifted by crane into position over the piles. The tubs create a watertight working area to install the steel pile cap structure and act as formwork for the concrete infill. The pile tub and infill concrete connects each group of four piles below the water to each pier that projects above the water.
Q: What's the next step?
A: From there, the V-shaped piers are built using access platforms attached to the pile caps. The piers are poured in two stages: in the first stage to the underside of the V and then in the second stage to both tops of the V. Stainless steel bearings are then installed on top of the pier heads, which will eventually support the bridge deck. There are two bearings on top of each pier, one on each side of the V.
Q: How is the deck constructed?
A: The deck is poured in individual segments, each about 20 metres long. They are constructed on site at the southern end of the bridge. Each has around 36 cubic metres of concrete. It is a relatively large pour and 19 segments will make up the bridge.
Q: What then when a deck segment is completed?
A: The deck is then pushed via hydraulic jacks across the top of the bearings into its final position using low-friction pads, which allow it to slide. The whole segment is moved 20 metres north and another 20 metre segment is constructed behind it. The process is then repeated again and the next segment put into place by the hydraulic jacks. Once all 19 segments are built there will be 360 metres of bridge and it will then be pushed into its final location.
Of course, while a lot of our attention is focused on the actual bridge construction,massive earth moving works are being carried out across the project site.
A huge amount of sandstone has been removed from the northern side of Illaroo Road which will eventually create the permanent northbound turning lane onto the highway,.
That rock has been transported to what was formally Bryce's paddock on Bolong Road and has been crushed and then reused in the project.
On the northern side of Bolong Road, work has been undertaken to change the boundary of the historic Illowra property. The beautiful old home can now be seen from the highway for the first time in a long while.
Work is progressing on the new crossing of Bomaderry Creek and excavation is well underway for the northern end of the bridge.
On the southern side of the river works are ongoing at the intersection of Bridge Road and the Princes Highway, and further south the highway edge in front of the Shoalhaven City Council administration building has been widened.
A new access road for residents from the Riverview Road area and surrounds, back onto the highway has also been constructed.
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Robert Crawford
Robert Crawford is a senior journalist at the South Coast Register, for Australian Community Media . Everyone's got a story, what's yours? Email robert.crawford@austcommunitymedia.com.au
Robert Crawford is a senior journalist at the South Coast Register, for Australian Community Media . Everyone's got a story, what's yours? Email robert.crawford@austcommunitymedia.com.au
