Tunnels

Why tunnels work

Tunnelling is becoming a popular solution as cities around the world look to expand their transport networks. They are very useful in locations where aboveground options are exhausted and communities place a high value on land at ground level.

Tunnels allow for effective, secure train operations and offer a viable alternative to an aboveground rail system. They save space and reduce cost. They also minimise potential environmental impacts on existing residential and business areas, compared to aboveground options.

Construction of tunnels

The most significant construction site for the Forrestfield-Airport Link will be near the main tunnel portal at Forrestfield. This area will feature the key infrastructure, including bentonite and slurry treatment plants, which will be used during the construction period to support the tunnel boring machines. The site will eventually be home to a new train station and car parking facilities.

Once the tunnel boring machines arrive, they will be launched from this site and will make their journey to Bayswater, constructing the tunnels along the way.

The tunnels are at varying depths with the deepest point being beneath the Swan River, where the roof of the tunnel will be approximately 25m below the riverbed. Overall, the depth of the tunnel will average 15m below the surface.   

Cross passages (allowing access between the tunnels) and emergency exits will be constructed at various points along the rail route.

Experience in building tunnels

Salini Impregilo, part of the joint venture with NRW to build the Forrestfield-Airport Link, has 100 years’ experience building tunnels and infrastructure around the globe. Their work to date includes 6830km of railways, 400km of metro systems and 1450km of underground works.

The company is experienced working in challenging environmental conditions, such as those found in Doha and Riyadh, where it has been involved in two of the biggest metro systems in the world.

Read more information about some of the company’s projects, either completed or underway.

130m

The length of the TBMs

60,000

The number of pre-cast concrete segments