PROJECT SPOTLIGHT
Piling through the cold
Keller Canada installed the foundation
piles in phases, beginning in February
2015 with the administrative offices
the first out of the chute, because those
offices were needed by mid-April.
Geotechnical field testing and
laboratory results indicated that the
subsurface conditions at the jobsite
consist of interbedded layers of loose
sand silts and soft, high-plastic silty
clays in the top five to eight metres,
followed by a series of soft to firm,
high-plasticity silty clay to a depth of
13 to 18 metres. Below this is a thick
layer of stiff, medium-plasticity clay
and silt tills, which the rig operators
could definitely sense when the augers
drilled into it. Finally, the geotechnical
investigation identified shale bedrock
at depths greater than 29 metres.
The field exploration also indicated
that the silty clay soils in the upper
15 metres have a high potential for
swelling. This means that fluctuating
water levels would cause shallow
foundations to undergo distress due to
volume changes in the soil, so shallow
foundation systems were not recommended
on the site. Due to the high
probability of ground water seepage
and/or sloughing conditions during
installation, conventional drilled,
cast-in-place concrete piles were not
recommended either.
Instead, Keller Canada installed 640
continuous flight auger piles for the
transit facility using Soilmec R-516 and
R-625 drill rigs. CFA piles are installed
by drilling a continuous flight hollow
stem auger into the ground, and then
pressure injecting concrete through the
shaft of the auger as it is extracted. This
eliminates any concerns of groundwater
seepage or sloughing, as the hole is
never left open without support. And
casings are not necessary with the CFA
drilling technique. Once the CFA pile
bores are completely filled with concrete,
steel reinforcement cages are
pushed down into the fresh concrete.
The CFA piles for the transit facility
had a diameter of 400 mm to 500 mm
and a depth ranging between 12 to
23.5 metres. The majority of the piles
were drilled deep into the stiff clay and
till layer but above the shale bedrock.
The deepest piles required the torque,
power and crowd force of the Soilmec
Warm spring weather and fast snowmelts quickly caused the jobsite to become
entrenched in mud, but Keller Canada still managed to install the piles ahead of schedule
will centralize key transit operations to
a single location with direct access to
the Circle Drive South Bridge, allowing
the city to move equipment, materials
and vehicles more efficiently.
The SCOC will also include the first
permanent snow management facility,
which will have the capacity to store up
to 1 million cubic meters of snow and
will feature an environmentally-safe,
cost-efficient meltwater collection site.
All building foundations for the new
SCOC were installed this spring by
Keller Canada, using Soilmec drill rigs.
a major upgrade with the construction
of a new Saskatoon Civic Operations
Centre (SCOC).
Located on 180 acres in the southwest
quadrant of Saskatoon, the SCOC
will replace a 100-year old transit facility
– the Caswell Hill “bus barns.” The
new transit facility will have room to
store 224 buses with the capacity for
future fleet growth. It will also feature
new administrative offices, fueling,
wash lanes, maintenance bays and
inspection pits. The 42,000 squaremeter,
steel framed transit building
PILING CANADA 45