Tunnel Lining

Approximately 9000 rings of concrete, each made up of six segments, were required to build the tunnels for the METRONET Forrestfield-Airport Link. 

A purpose-built segment production facility was commissioned at Forrestfield in April 2017. Two years on, in April 2019, the production of all segments - totalling more than 54,000 - was completed. 

Testing the concrete

As part of preparations for the manufacture of the pre-cast segments, the concrete underwent a series of tests to ensure it met the required standards for strength and durability.

Prior to installing the first segment rings, fire testing on the concrete for this project was completed in Victoria, Australia and Germany. 

Pre-cast segments

The pre-cast segments were constructed using steel moulds and a concrete mix specifically designed to meet the specifications of this project. A carousel system was used to move the moulds through various workstations. After fitting materials such as gaskets and installing steel reinforcement, the concrete was poured and trowelled before being left to steam cure for several hours. Segments then underwent a series of assessments before being painted and stored for transport to the High Wycombe Station, Airport Central Station and Redcliffe Station sites.

A purpose-built multi-service vehicle (MSV) was used to cart the segments to the tunnel boring machines.

Watch a video on how the tunnel segments were constructed.

Our segments are award-winning

 In July 2019, the project received the 2019 Concrete Institute of Australia (WA) Award for Excellence in the Technology and Innovation Category.

The judges said the team had gone “well and truly above and beyond what is the norm” in the production of tunnel segments for the Forrestfield-Airport Link.

“The tunnel segment lining has been designed and manufactured to deliver an infrastructure project that performs above industry best practice and standards,” the judges said.

Some of the production features that impressed the judges include:

• The solution used for the manufacture of the segments was based on a hybrid system using steel fibre-reinforced concrete and light steel reinforcement rebar cages.
• Polypropylene fibres were incorporated within the concrete mix to comply with the fire resistance requirements.
• The mix-design was developed based on triple-blend cementitious materials. A customised production plant was established to produce the segments, along with a dedicated concrete batching plant.