A massive tunnelling project for a new GO Train route under the 401 is in progress.

Last week Metrolinx blogged how the underground operation under the Highway 401 and Highway 409, to build the GO train tunnel would happen without disrupting traffic flow above.

This tunnelling is to provide the province with the two-way, all-day train service on the GO Kitchener line. The Kitchener corridor will have two tunnels side-by-side, accommodating one track each. The tunnels will run 180 metres under the highway intersection.

The interchange of Highway 401 and Highway 409 is one of the busiest sections of highway in North America, and tunnelling has begun under 21 lanes of traffic above.

In order to keep traffic flow going strong, Metrolinx and Toronto Tunnel Partners are using innovative technology for this subterranean project.

  • SEM (sequential excavation method): is a modern tunnel design and construction method. Earth, rock and debris are removed steadily at a one-metre pace, with the tunnel divided into sections. Machinery like the ‘scooptram’ front end loader to haul away material five tonnes at a time is used. 
  • Excavation with Shoring: during excavation, the exposed area is immediately supported by spraying a layer of ‘shotcrete’, by a shotcrete robot, after which a reinforced temporary lining called “welded wire fabric”. Then lattice girders are installed as an additional measure.
  • Canopy tubes: in spring, canopy tubes were installed using auger boring. These tubes are 12-metre-long metal hydraulically pushed by a giant drill under the highway to encase the tunnel. As the augers turn they expel the material they excavate from out of them. These canopy tubes are the solid structure of the tunnel, in order for the passage of the tunnel to be bored through.  
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Photo source: Metrolinx blog.

Infrastructure upgrades for the Kitchener corridor included this double-tunnel as well as replacing footings of retaining walls that support the ramp from Highway 409 eastbound to Highway 401 eastbound. The tunnels will accommodate future electrification of the railways, signalling and communications infrastructure inside.

These tunnels demand an excavation of 31,000 cubic metres of material – equivalent to 12 Olympic-size swimming pools, and will use over 8,000 cubic metres of shotcrete.

This massive undertaking may be going on unbeknownst to many who travel over it, and the project is expected to be completed in 2021.

For more information, check out Metrolinx’s blog post here.