This spring Vancouver will see two special residents arrive — tunnel boring machines for the SkyTrain’s Millennium Line Broadway Extension project.
The Broadway Subway Project is a 5.7-kilometre extension of the Millennium Line, from VCC-Clark Station to Broadway and Arbutus.
Approximately 700 metres will be elevated, extending from VCC-Clark Station to a tunnel portal near Great Northern Way. Five kilometres will be tunnelled below the Broadway Corridor from Great Northern Way to Arbutus Street. Six underground stations will connect communities and the region, including a direct underground connection to the Canada Line at Cambie Street. The project is expected to open to passengers in 2025.
Digging will be carried out by two specially built machines ordered from Europe.
“The bid process for the tunnel boring machines (TBMs) was a very competitive and global process that resulted in Herrenknecht in Germany being awarded the work,” said a spokesperson for the Ministry of Transportation and Infrastructure. “The earth-pressure-balanced TBMs for the Broadway Subway Project are being built to certain specifications for the type of construction planned as well as the expected geophysical conditions from Great Northern Way to Arbutus.”
According to Herrenknecht, softer soils require earth pressure support as machines with earth pressure balance shields turn the excavated material into a soil paste that is used as a pliable, plastic support medium.
The company noted this makes it possible to balance the pressure conditions at the tunnel face, avoids uncontrolled inflow of soil into the machine and creates the conditions for rapid tunnelling with minimum settlement.
The ministry explained the two machines, each six metres in diameter, will be launched separately at the Great Northern Way-Emily Carr station and tunnel to Cypress Street, where they will be disassembled and removed through an excavation shaft. Disassembly will take around 60 days. They will conduct boring operations for approximately a year.
The ministry stated the tunnels they bore will be approximately 15 metres below ground to a max of 20 metres at Broadway-City Hall. The machines are capable of advancing approximately 18 metres per day.
Each machine is 150 metres long, includes crew facilities and weights roughly 907,000 kilograms. The machines require around a dozen trained staff to operate. The ministry expects them to generate a total of approximately 200,000 cubic metres of soil that will be removed through the tunnel on a conveyor system at Great Northern Way.
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