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subway construction techniques

Tunnelling Process

Tired of the same old topics of conversation when you get together with family and friends? Next time, why not impress them with your newly acquired knowledge of how the vivaNext subway extensions will be constructed?

Surprisingly, few people know that there are many different elements to consider when building a subway, including which construction technique to use. As it turns out, that mostly depends on where one is digging.

Now for the boring stuff. Tunnel boring, that is. It’s one of the two main techniques used to build a subway. The second one is cut-and-cover.

The tunnel boring technique is generally used for deeper applications such as between stations. Because the tunnels are literally bored out below the surface, there is no disruption at the ground level except at the entry and exit points of the machinery.

Cut-and-cover, on the other hand, is the technique generally used for shallow applications such as station locations. In this case, there is some disruption at the ground level and temporary decking is installed when necessary to accommodate vehicular and pedestrian traffic.

In addition to tunnels and stations, the construction of a subway involves building a number of other special structures located above and below ground. These include crossovers, triple track structures, tail tracks, electrical substations, emergency exit buildings, vent shafts, bus and commuter rail terminals, parking lots, passenger pick-up and drop-off facilities, and pedestrian entrances.

spadina subway

Yonge Subway Extension

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awaiting funding

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geotechnical tests on Yonge > Jul-Aug 2009

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Yonge Subway Extension

The planned Yonge subway extension will extend 7.4 kilometres north from Finch Station to the Richmond Hill/Langstaff Urban Growth Centre at Highway 7, and will include five stations. This urban centre will be a major transit hub where transit riders will be able to make seamless and convenient connections to GO Trains, GO Buses, TTC Subway, YRT/Viva buses, the future 407 Transitway and other transit services. To put it into perspective – a Union Station of the north!

In April 2009, the Ontario Ministry of the Environment unconditionally approved the Environmental Project Report [and addendum] for the Yonge subway extension. In 2012, the Conceptual Design Study that looked at specific engineering elements was completed and approved by the Toronto Transit Commission and The Regional Municipality of York.

What really sets this project apart from other proposed transit projects is the role it plays in the GTHA’s overall transportation network – roads and transit. No other project can do more to advance the need for improving transportation in the GTHA. This project can combine with market forces to unleash significant economic, environment and development benefits.

Whether from a plane, from the ground or underground on the subway, it is easy to see that Yonge Street is one of the main arteries in the GTHA – and has been for generations. That is why it is vital to move this project forward along with other proposed transit projects, steadily improving the overall transportation network.

Dealing with existing congestion on the Yonge line is a challenge, and while over 60% additional capacity is already being added to Yonge Subway from these current projects now underway, growth beyond 2030 will continue to create capacity concerns on the Yonge line:

  • Automatic Train Control [adds 36% capacity]
  • New Signals [adds 10% capacity]
  • Six-car Trainsets – “Rocket Trains” [adds 10% capacity]
  • Toronto-York Spadina Subway Extension [adds 8% capacity]

With the environmental assessment approved, the conceptual design study completed and its identification as a priority project by Metrolinx in their next wave of funding projects, this project is truly in a state of readiness for capital funding and provides the critical missing link to the GTHA transit network.

To that end, we are working together with Metrolinx, TTC and City of Toronto on a Regional Relief Strategy to develop a comprehensive plan to improve transit along the Yonge corridor and improve the daily lives of people for generations to come. This is a comprehensive approach that is looking at all options, including service improvements, fare and network integration, and new rapid transit projects so that you can go where you want, when you want – comfortably, conveniently and reliably. Future land use, development and other benefits of different alternatives will be considered as phasing for new projects and service improvements will be recommended.

To read about why the Yonge Subway extension to Highway 7 is considered a top priority, see The Missing Link.


Tunnelling Process

Subway Construction Techniques

Get the scoop on what goes on underground when building a subway.

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