NorthLink WA Stage 1 - Southern Section

Reinforced Earth® TerraTilt®

Perth, WA, Australia
Main Roads WA
John Holland Pty Ltd
Nov 2016 - Jan 2018

The $1.02 billion NorthLink WA Project, jointly funded by the Federal and State Government, takes traffic off local roads and onto the Tonkin Highway. This means local roads will be used for local traffic and those who live and work locally will experience a safer, more peaceful environment. It also provides an efficient alternative freight route, taking about 80 per cent of trucks away from the Great Northern Highway.

 The southern section of Northlink WA provides a freeway-standard, free-flowing link from Collier Road through to Reid Highway via Tonkin Highway.

Works included:

-     Grade separations at Benara Road, Morley Drive and Collier Road

-     4m wide shared path along Tonkin Highway from Guildford Road to Reid Highway

The Reinforced Earth Company (RECO) was awarded the design and supply of the abutment walls at the Morley Drive and Benara Road intersections as well as additional retaining walls. The total of Reinforced Earth® walls supplied for the project was 4788m2.


-       Re-design an in-situ counterfort retaining wall to a Reinforced Earth® wall that can accommodate large horizontal traffic barrier loads.

-       Large horizontal bridge loads

-       Architectural finish, circle pattern

-       Curved abutment panels with architectural finish, circle pattern


RECO was able to develop a modified traffic barrier and Reinforced Earth® wall interaction that restrained any horizontal loads from the traffic barriers being transferred to the wall itself.  The system incorporates a column and capping beam that the traffic barrier is cast on top of.  The capping beam has soil reinforcement connected to it and it is this, along with the columns, that restrain the horizontal loading.  Due to traffic barrier loads not being transferred to the wall, we were able to use our standard TerraTilt® panel design with optimised thickness and reinforcement. Overall, this optimisation significantly reduced the client’s costs for the wall, especially when comparing it to the original design of an in-situ counterfort wall.  Significant design checks were carried out to ensure the capacity of the column and capping beam soil reinforcement system was adequate for restraining the traffic barrier loads.  Similarly, soil reinforcement was connected to the capping beams at each bridge abutment to restrain the large horizontal loading caused by braking vehicles. 

To achieve the architectural finish, patterns were laser cut out of steel plate and welded to 12m flat casting beds.  This resulted in an accurate, identical pattern across all the panels.

The architectural finish on the curved wingwalls of the Benara Road abutments was achieved using a steel mould that was fabricated specifically for the project to ensure the radius of the required curve was met as well as the positioning of the circular pattern across this curve.   

By removing the traffic lights and creating the grade separations along Tonkin Highway, traffic flow has improved, leading to safer and quicker journeys for commuters, residents and the freight industry.

Project Specifications

Reinforced Earth® TerraTilt®
6 x Reinforced Earth® Bridge abutments, 3 Reinforced Earth® retaining walls
4,788 sqm (total)
9.8 m
Design Load
20kPa surcharge
Design Life
100 years
Circular architectural finish on both flat and curved panels

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