San Francisco Central Subway and the Philadelphia Museum
of Art.
“The flat jack was specifically made for areas that have
very little clearance,” said Stephen Cireco, president at WB
Equipment. “When deflated, the jacks are only 1.3 inches tall
so, in tight spaces, they have proven to be extremely useful.
And, unlike normal hydraulic jacks, these jacks also have the
ability to become a permanent part of your structure.”
When installing the underpinning piles, PCL would pour
a cast-in-place pile next to the existing building foundation.
The cast-in-place pile would then have a concrete pile cap on
top that was engineered to a very specific shape in order to
reach under the existing building foundation, leaving a narrow
space between the top of the pile cap and the underside of the
existing foundation. The flat jacks were then placed at strategic
locations inside the gap to ensure there wasn’t any sinkage
when the roof load was transferred from the existing building
foundation to the new underpinning piles.
The flat jacks were then filled with epoxy grout up to a precise
amount of pressure that translated to a specific amount
of force pushing outward on the exterior surface of the bag,
which then corresponded to a certain weight on the new
underpinning pile. The remaining space between the underpinning
pile and the foundation was then grouted solid.
“The flat jack is basically a metal balloon that sits in
between two objects,” said Park. “You fill the flat jack up with
liquid grout to a certain level, tie off both ends of the ‘balloon’
and – over the course of 24 hours – the grout that’s inside the
flat jack will harden and become a completely solid object.”
As is common with the unfamiliar, there is a natural tendency
to be hesitant when using something new. As such, flat
jacks were not the first technology PCL considered. The company
explored a number of different options before choosing
flat jacks, such as the use of steel plates or hydraulic jacks
that could temporarily pre-load the underpinning piles as the
space between the new underpinning piles and the existing
foundation was grouted.
“To be honest, since I had never worked with flat jacks
before, I looked into a number of different options instead of
using them,” said Park. “But in terms of the actual work that
took place on site, it ended up being very easy to use the flat
jacks and I know that if I were to ever run into a similar situation,
I would use them again in a heartbeat. Flat jacks were
far and above the most economical solution in providing the
pre-loading detail we required.”
The pile cap on PCL’s cast-in-place piles is wider than the
pile itself and, when installing the flat jack, it was critical
that the jack be placed on the centre line of the pile so the
force from above would be transferred directly onto the pile.
One of the unforeseen challenges for the project was that the
pressure gauge on the flat jack was positioned in such a way
that the jack could not be placed on the pile cap’s centre line.
Fortunately – with the blessing of the WB Equipment
supervisor on site – the solution was to simply remove the
gauge and flip it around to a different orientation to allow
PCL the ability to reposition the flat jack a couple of inches
over, along the centre line.
“It really just meant that some creative and collaborative
engineering needed to be used to get that thing to fit exactly
where it was supposed to go,” said Park. “But it goes to show
that even on large buildings of thousands of square feet, every
single inch or two has the potential to affect the success of a
project or impact the performance of the building.”
PCL recognizes that its most valuable asset is its employees
and, as such, the creation of a safe and healthy work
environment is one of the organization’s most central guiding
principles. PCL refuses to compromise on the safety of its
people and its safety program raises the bar for the construction
industry as it strives to achieve zero safety incidents
throughout the course of each and every one of its projects.
PCL’s Safety Observation System teaches employees to
recognize and eliminate hazards and dangerous conditions
by correcting unsafe behaviour through positive coaching.
The company also makes its policies, procedures, guidelines
and practices for performing work safely readily available for
all its employees through the use of its comprehensive health,
safety and environment manuals.
“We will hold extensive safety orientations with all of
our projects, along with daily pre-job safety inspection that
we renew at every break,” said Park. “As the work changes
for each activity we do over the course of a project, we
will provide additional jobsite-specific Health, Safety and
Environment Operating Procedures (HSEOP). Whether it
is for cast-in-place piles, pre-cast piles, pile cap forming or
excavation, each one of the tasks we undertake will have its
own particular HSEOP.”
Although the LEED® certification process is still underway,
it is expected that the new expansion will achieve at
least LEED® Silver certification through the Canada Green
Building Council, clearly demonstrating the sustainable
approach that was taken in the design, construction and current
operation of the building
“Winnipeg Transit is a 24/7, 365 days a year operation and
it is an essential service for a lot of Winnipeggers in getting
from Point A to Point B across the city,” said Park. “To say
that this project has been a feather in my cap would be a tremendous
understatement. It’s been a privilege to play even
a small role in helping Transit provide this service, and this
project has proven to be a phenomenal opportunity for both
myself and PCL.”
GREAT CANADIAN PROJECTS
“Unlike normal hydraulic jacks, flat jacks also have the
ability to become a permanent part of your structure.”
– Stephen Cireco, WB Equipment
64 Q1 2020 www.pilingcanada.ca
/www.pilingcanada.ca
