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 houses the key infrastructure, including bentonite and slurry treatment plants, which support the tunnel boring machines. The site will eventually be home to a new train station, car parking facilities and further transit-orientated development.

The tunnel boring machines were launched from this site in 2017 and are making their journey to Bayswater, constructing the tunnels along the way. The tunnels vary in depth along the route, with the deepest point being beneath the Swan River, where the roof of the tunnel will be approximately 26m below the riverbed. Overall, the depth of the tunnels 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, is a world leader in complex construction with more than 110 years’ experience building tunnels and infrastructure around the globe. Their work to date includes the delivery of 1587km of tunnels and 7534km of metros and railways. The company is experienced working in challenging environmental conditions in major cities such as Doha, Qatar and Riyadh, Saudi Arabia, where they have been involved in two of the biggest metro systems in the world.

Read more information about some of the company’s current or completed projects.