| What we're doing |
What it involves |
| Bridge Sliding |
Bridge sliding is the process of literally sliding a pre-cast bridge
into place. The bridge pieces are moved along slide paths into position
by the power of computerized high-speed tandem hydraulic jacks. This
process is a great advantage in a rail corridor because it only requires
very short periods of track possession, which means the bridge sliding
can take place without major disruptions to train schedules. Four bridge
spans weighing a total of some 10,000 tonnes will be slid into their
final positions at the West Toronto Diamond during the final phase of
construction. |
| Bridge Span Installation |
The bridge span installation process begins off site, at a mill
where pieces of the span are pre-built. The raw materials are tested for
quality assurance, and then cut and welded together. Once the pieces are
ready, they are assembled to ensure that none of the pieces are missing.
The bridge is then unassembled and transported to the construction site,
where a crane is used to lift the pieces into place. Main girders are
installed first, followed by the panels. A cover plate is used to cover
the abutment and handrails are installed. Once the bridge span is
waterproofed and the ballast material has been installed, the tracks and
ties can be laid. |
| Clearing and Grubbing |
Prior to construction, clearing and grubbing of the site area is
done to ensure a clean and safe work area. Organic matter such as bush,
trees and shrubbery are cut down and removed in accordance with the City
of Toronto by-laws. Debris and garbage is also removed off site, making
the work area free of any obstructions. The equipment used to conduct
this work can include chain saws, wood chippers, loaders and dump
trucks. |
| Excavation |
Essentially, excavation means digging or removing soil; what varies
is the function of the dig. At a construction site, excavation can take
place at nearly all phases of a project for different reasons. For
example, we excavate when we dig up the dirt around buried utilities
such as wires, cables and water mains that need to be relocated before
major construction can begin. We also excavate as an entire phase of
construction where a tunnel is being dug in order to lower the rail
corridor below grade. However, before any excavators can get to work,
temporary shoring or retaining walls must already be in place to keep
the soil from backfilling into the hole as it is being removed. |
| Forming of Walls |
Forming of walls occurs when concrete walls are poured in place.
Wood or aluminium forms are set into place at the locations where the
walls will be going and concrete is poured in between. The concrete is
allowed to cure or harden and then the forms are removed, leaving behind
the concrete walls. At the deepest point of the Weston Tunnel, the
tunnel walls will be 12 metre deep. |
| Forming of Urban Surface |
An urban surface will be created by the construction of the lid for
the Weston Tunnel. This will be built by installing scaffolding below
the surface and putting forms into place in 20 metre sections. Concrete
will then be poured into the forms and left to cure and then the
scaffolding will be removed. The concrete will be approximately 1 metre
thick and will be strong enough to support a significant amount of
weight that would allow for earth and grass to be put in place, and
allow the surface to be used for other purposes. |
| Installation of Struts |
Struts provide outward-facing support for retaining walls that are
required for the lowered rail corridor. The struts are lifted into place using a crane and then secured into the retain wall using bolts. For the Strachan Avenue Overpass, struts will span across
the corridor from the section between Stanley Terrace and Shaw Street to
support the north and south retaining walls. |
| Jack and Bore |
This is a method that installs a pipe through the earth while
simultaneously removing earth spoil from the casing through a rotating
auger inside the casing. Also referred to as auger boring or horizontal
boring, it ensures little or no disruption to surrounding businesses,
residents or the environment. |
| Pile Installation |
Piles come in different shapes and sizes and are installed in
different ways, depending on what is appropriate for local ground
conditions and the type of structure they are being used to build. At
the West Toronto Diamond, interlocking steel pipe-piles and sheet-piles
are driven into ground using vibration, push and impact methods to
create the retaining wall for the lowered corridor and to hold up the
two bridges. At other worksites along the corridor, some piles will be
formed by pouring concrete into a hole, which is called auger cast in
place piling. Regardless of the shape and size, all piles have a similar
function: they form a foundation and distribute the weight load of the
bridge, tunnel or structure being built. |
| Pile Validation |
Pile validation is the process of removing soil from within pipe
piles and filling them with concrete and other sealing materials to
create a water tight foundation wall. Large crane mounted augers and
drum cleaners remove the dirt and sweep the sides of the piles and then
a trailer mounted concrete pump fills them with concrete and other
sealing materials, such as types of grout to fill in tight spaces. At
the West Toronto Diamond, pile validation defines the second last phase
of construction – it follows pile installation and must be complete
before excavation can occur in the same area. |
| Road Cuts |
A road cut is the process of cutting into the road, and is needed to
expose any water or sewer pipe lines that exist beneath a paved road.
Prior to actually cutting the road, a permit is required from the proper
authorities, such as the City of Toronto. This work is done in
conjunction with utility relocation work for water and sewer pipe lines. |
| Shoring |
Shoring is used in construction to provide support against the
weight of soil to allow excavation to take place safely and prevent
cave-ins. This will be used for underground utility work, such as at
Denison Road and the Lawrence Avenue Bridge. It will also be used in the
construction of the Weston Tunnel where steel columns will be augured
into the ground with vertical wooden beams used to create the shoring
wall. |
| Signal Installation |
Signalling systems are used to move trains efficiently and
communicate the location of trains on the tracks. The Georgetown South
Corridor is undergoing a full signal upgrade to accommodate the service
improvements that will be taking place. The upgrades to the signalling
system will allow the trains to run at shorter intervals in order to
accommodate the increase in service in GO Trains and the new Air Rail
Link service. Along the corridor, signals are in place approximately 1
kilometre apart at key intervals such as crossovers and level crossings.
Signals include a mix of hard wire and wireless transmission systems
providing redundancies in case of a failure. |
| Signal Maintenance |
Regular maintenance of signals ensures that the system is in full
working order. Manual checks of the tracks and signals occur monthly to
confirm that the tracks and signals are clear of debris and operating as
expected. A train simulator device is used to determine that the system
is operating as expected. The removal of level crossings taking place in
the Georgetown South Project, such as those at Strachan Avenue and
Carlingview Drive, will dramatically increase the safety and signal
reliability. |
| Tie-back Installation |
Tie-backs are installed by the contractor to hold up walls against
pressure pushing them inward. They can be made from wire or rods that
extend into rock or earth. Tie-backs will be used to support several
shoring walls throughout the GTS Project, such as the Weston Tunnel. The
tie-backs used for the Weston Tunnel will be approximately 13 metres
long and will extend down into the ground to support the temporary
shoring wall. Each tie-back will consist of six to seven cables, each a
half inch in diameter. When the tie-back support is no longer needed,
they will be cut off and left in place. |
| Track Shifts/Track Detours |
A track shift is when train tracks are moved from their original
location to another. Essentially, the old sets of tracks are removed and
a new set of tracks are installed to allow trains to travel on. Often,
this is done to allow construction workers to work in the area of the
original tracks. Depending on the type of train corridor, this work can
be done anytime a train is not passing. If it is a live corridor, this
work is usually done at night, or at other times when trains are not
travelling through the corridor. To shift a track, the material for the
new track is brought on site, ballast material is put down, tracks are
laid, and a tamper is used to make sure the ground is level and the soil
is packed. A track stabilizer puts the finishing touches and pinches
everything into place using vibrations. Track shifts/detours are done
prior to major excavation. Once the excavation is complete the tracks
are put back into their original location. For example, at the Weston
Tunnel, tracks will be shifted to allow excavation on the tunnel itself
to be completed. After the tunnel is created, the tracks will be placed
back in the same location. |
| Utility Relocation |
Prior to construction along the GO Transit train corridor, any fibre
optic cables and utilities need to be removed from under the rail
corridor. Often, electric, telephone and cable companies have their
lines buried beneath the train tracks or on GO Transit property. Each
respective utility company is responsible for the relocation of their
own lines from the existing location, to one that is out of the way of
construction. Coordination of this work between each utility company is
done in cooperation with the contract administrator. Toronto Hydro and
gas companies are also part of the utility relocation phase. For
example, if work is being done near or on a road, there are water, sewer
and gas mains which run into each residential/commercial property from
the main municipal connection underneath. Once again, work is conducted
by each respective company to remove pipes which are in the way of the
build. One example of this is at the Denison Road Underpass, where the
contract administrator coordinates work with Toronto Hydro and Enbridge.
To conduct this work, the road is cut and soil is excavated to expose
pipe lines using a hydrovac and a backhoe. |
