Nicholson Road Bridge Over Rail Project


TerraTilt®, TerraPlus® and TerraTrel®

Location:
Perth, WA, Australia
Owner:
Main Roads WA
Consultants:
Arup
Contractor:
CPB Contractors
Construction:
May 2017 - Mar 2018

Jointly funded by the Australian ($13.7m) and State ($13.7m) Governments, a road bridge over the railway line on Nicholson Road between Bannister Road and Garden Street in Canning Vale is now completed.

The works included:

-    A six-lane road bridge over rail

-    Road infrastructure including safety barriers, drainage, signs, screen/noise walls, pavement marking and street lighting

-    Modifying the existing road to maintain traffic flows during construction

-   Pedestrian and cycling infrastructure that includes a pedestrian underpass and a path on the east side of the new bridge.

The Reinforced Earth Company (RECO) was awarded the design and supply of the abutment walls, wing walls and other retaining walls on the project. The total of concrete facing Reinforced Earth® walls supplied for the project was 5293m2. On top of this, a further 437m2 of temporary Reinforced Earth® wire walls were supplied.

-       Geotechnical report showing large pockets of clay beneath the walls and resulting high potential for differential settlements

-       Staging of works to maintain traffic flow

-       Large temporary crane loadings on top of the abutments

-       Reinforced Earth® walls with noise/screen walls directly on top

Early in the design process, RECO identified the potential issues that could be caused from the differential settlement highlighted in the geotechnical report.  Further site investigations and desktop studies were carried out by RECO to analyse and confirm what design requirements were needed to mitigate these issues.  This resulted in a maximum retained fill height of 4m being applied to our full height TerraTilt® walls.  Anything higher than this required our segmental TerraPlus® system to be applied.

To assist in the staging of the works for CPB, and allowing for continuous traffic flow along Nicholson Road, RECO designed and supplied temporary TerraTrel® wire walls. These walls enabled construction of the entire bridge structure and road whilst the installation of only one side of each abutments wing walls was underway.

Once the roads over the bridge were complete, traffic was able to be switched and the remaining wing walls and retaining walls were constructed in what was previously the road alignment.

Because of the small project footprint, the bridge beams were required to be lifted in place by 3 cranes positioned on top of the abutments as can also be seen in the picture above.  Detailed assessment was carried out by RECO engineers and the Reinforced Earth® walls were able to be designed specifically to withstand the high crane loads applied.   

As an alternative to the standard noise/screen wall footings directly behind the walls, RECO was able to design the retaining walls with a 2m cantilever above the finished ground surface. This cantilevered section, supported only by the soil reinforcement of wall, was finished with a class 2 finish on both sides and was painted to become the noise/screen wall.

The new road bridge takes Nicholson Road over the Midland to Fremantle Freight Railway and removes the previously existing railway level crossing, enhancing safety and transport efficiencies.

Project Specifications

System
TerraTilt®, TerraPlus® and TerraTrel®
Structure
2 x Reinforced Earth® Bridge abutments including wingwalls, underpass wingwalls, additional retaining walls and noise/screen walls.
Area
5,293 sqm (total)
Height
10 m (max)
Design Load
20kPa surcharge - Crane Loading
Design Life
100 years
Finish
Class 2, plain grey, painted on site

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