Ontario Construction News staff writer
After several months of digging, crews on the Hwy. 401 and 409 Rail Tunnels project finally saw daylight at the end of Tunnel One. The infrastructure supports GO expansion and will transform rush hour commuter service to two-way, all-day train service on the Kitchener line.
The breakthrough moment is a key achievement for the project, and Metrolinx’s contractor, Toronto Tunnel Partners.
Tunnel One is approximately 186 metres long with a diameter measuring 11 metres, which is about 36 feet – taller than an average three storey home.
According to a Metrolinx blog post, approximately 35,000 cubic metres of material were hauled away by trucks in an organized and timely sequence to keep the project progressing as efficiently as possible. The sheer volume of material removed could fill 14 Olympic sized swimming pools, Metrolinx stated in the blog.
The new tunnels are being constructed using the Sequential Excavation Method (SEM), a way of tunnelling that splits the excavation into segments. This approach empties the tunnel in bite size amounts. The upper portion of the tunnel is considered one segment and the lower section of the tunnel is another segment.
The crew applies shotcrete between segments, which is concrete that is sprayed onto the inner surface of the tunnel to provide reinforcement and strength to retain its shape.
Crews have already sprayed approximately 3,400 m3 of shotcrete. A concrete truck shuttles concrete to a robotic shotcrete machine to manage this fundamental layer of work. The technology provides the proper pressure to set the concrete in place.
Work began in October 2019, and Tunnel Two is “progressing well.” When completed by the end of 2020, the total length of the two rail tunnels combined will be approximately 360 metres and the design will allow Metrolinx to build two additional tracks in the future.
Metrolinx is building twin tunnels, less than three metres underneath Highways 401 and 409 – all without disrupting the continuous traffic flow above.
For a look at the work inside one of the tunnels, click here.