January/February 2023 - 71

FEATURE ARTICLE
Complex underground work for new light rail tunnels
AN OUTSTANDING PROJECT AWARD RUNNER UP
Eglinton Crosstown - Over and Under the Existing Subway
Cedarvale Station is one of 25 new
Eglinton Crosstown light rail transit
(ECLRT) stations along Eglinton Avenue
in Toronto. It is an interchange station
with the existing Toronto Transit Commission
(TTC) University subway line
and is located at the intersection of two
major thoroughfares. The new LRT
tunnels run below the existing Yonge
Spadina subway line and required total
excavation depths of 20 m (65 ft) to facilitate
construction of the new station.
TBM Exit and Launch Shafts
The TTC would not allow the tunnel
boring machines (TBMs) to tunnel
below the existing subway line due to
concerns regarding vibration and
settlement risk that could cause a
disruption in service. Instead, a TBM
exit shaft was constructed west of the
existing subway line and a TBM
launch shaft was constructed east of
the subway line, with the future
station to be built in between. These
shafts formed part of the advance
tunnelling contract awarded to Crosstown
Transit Constructors (Kenaidan
Contracting, Obayashi Canada, Technicore
Underground and Kenny Construction
Company). These shafts were
constructed by Deep Foundations
Contractors, now Green Infrastructure
Group (GIP) based out of Toronto, and
were designed by Isherwood Geostructural
Engineers.
To advance the schedule of the
tunnelling operations, it was decided
by the tunnelling project team to hoist
the still assembled TBM out of the exit
shaft via a large gantry crane provided
by Mammoet Canada. Due to limited
space available to support the gantry
crane, the designer and crane provider
worked together on a solution to
support one side of the gantry crane on
the exit and launch shaft secant pile
walls, adding loads in excess of
2,000 kN (460 kips) to the shoring
walls that travel along the wall at the
gantry leg location. The TBM was then
placed on a specialized hydraulic
trailer used to balance ground pressure,
to traverse 100 m (330 ft) along
Eglinton Avenue, above ground and the
existing subway line, before being
lowered via a second gantry assembly
into the launch shaft, again supported
on the launch shaft secant pile walls.
AUTHORS Shawna Munn, P.Eng., Isherwood Geostructural Engineers, and Sarah Speir, P.Eng., Crosslinx Transit Solutions
DEEP FOUNDATIONS * JAN/FEB 2023 * 71

January/February 2023

Table of Contents for the Digital Edition of January/February 2023

TOC
January/February 2023 - Intro
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January/February 2023 - TOC
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