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Helical Pile Foundation Case Study
One of the extraordinary benefits of helical pile foundations is the fact they can be configured to suit virtually any project, in any location. VersaPile's team has installed helical pile foundations for everything from power transmission lines in mucky fields to, in today's case study, inside a nearly 100 year-old heritage building in a busy city.
This project stands out to me because it perfectly demonstrates how versatile helical pile foundations can be.
From tight-access areas (like the inside of a building) to building sites located in environmentally-sensitive regions, it's the versatility of helical piles that are making them a favorite with engineers.
When an ambitious developer decided to save a 91 year-old heritage building and give it new life as a unique condo, they discovered typical driven or open caissons foundations wouldn't work.
The success of their project hinged on finding a solution.
With the fate of a century-old heritage building (and anticipated condo project) in question, we joined the developer's existing team of experts to find the answer.
Our team would ultimately deliver a foundation solution that could not only handle design loads of 150kips per-pile and was capable of penetrating dense till, but could be installed in some of the tightest confines you'll see on a job site.
The Academy Lanes building in Winnipeg, Manitoba, is a historic building with an important place in the cities' story. But, it wasn't always called the Academy Lanes. Originally named the Uptown Theater, it was built from 1930 to 1931 by architect Max Blankstein.
It was an immediate hit and crowds of well-dressed movie lovers flocked to the unique building to enjoy the latest flicks from Hollywood.
The Uptown Theater would eventually change from a theater into a bowling alley in the 1960's. Renamed to Academy Uptown Lanes, the building earned a designation as an official Canadian Historic Place in 1986. It would continue operating as a bowling alley all the way until 2018, when the doors were closed after more than 50 years of operation.
Plans were soon made to give the Academy Lanes new life as a unique multi-use building. The design called for the unsalvageable interior to be completely replaced with modern retail and condo housing, while retaining all of the historic value and character on the exterior.
This was much easier said than done.
Gutting an almost 100 year-old building on the inside while leaving no trace outside was going to take some seriously clever planning.
Due to the building's designation as a heritage structure, the new developers had to follow extremely strict rules regarding what changes could be made.
Teams from Concorde Projects, Crosier Kilgour & Partners, and Wood PLC, had been given the task of transforming an iconic building into modern shopping and housing while retaining the character. Exterior changes had to be kept virtually undetectable, so creating holes in the roof or altering the facade was completely off-limits.
The final design called for a new structure to be built inside the heritage building, leaving the beautiful facade untouched but bringing the interior into the 21st century.
From the beginning, it was clear to the teams that the foundation was going to be a big question to answer as the usual solutions weren't going to work.
This project was unique in that the interior structure that would house the retail and condo units needed to, essentially, have its own separate foundation. There was no way the 90+ year-old foundation that held up the existing building would be able to handle the new loads.
Preliminary designs called for loads of 150kips per pile. However, as they assessed their options, the structural engineers were faced with some big challenges.
Driven piles were out of the question due to space constraints and the dangerous vibrations they could create in the old building.
Open caisson piles were examined as a potential solution. However, superficial layers of rumble and sand in the overburden would have made excavating and hauling the material difficult and expensive.
The teams were stuck and needed a better foundation option, and soon. If they couldn't find something that would solve the foundation question, the whole project would be thrown into chaos.
It was at this point that VersaPile was engaged to help Concorde Projects, Crosier Kilgour & Partners, and Wood PLC, determine a foundation solution for this highly challenging project.
The helical pile foundation had to be strong enough to support the column strength requirements of the structure, but durable enough to penetrate the dense till. It also needed to provide enough surface area to the soil to distribute the loads, while still being small enough that we could install them with virtually no clearance.
Crosier Kilgour & Partners, offering structural engineering services for Concorde Projects, used the feedback from Wood PLC and VersaPile to design helical pile groups that would meet the design loads.
Two sizes of helical piles were needed for this project. Under the main structure, 4-1/2" diameter piles with a single 16" helix were selected. For the vestibule, slightly smaller piles were sufficient at 3-1/2" diameter with a single 12" helix.
Each pile, regardless of location, would be installed to refusal on dense glacial till. An on-site engineer would record data for each pile that went in the ground to ensure performance.
The total number of helical piles that were ultimately required for this project were:
● 117 piles for the condo● 24 piles for the vestibule● 141 helical piles in total
Helical piles were an ideal foundation solution for this project because they:
● Required no excavation, which eliminated the cost and hassle of hauling spoils out of the building● Easily met the load requirements with a compact and non-invasive design● Created no damaging vibrations on installation that would threaten the historic structure● Could be closely monitored during installation by on-site engineers and the performance data saved for later reference● Were easy to maneuver in the extremely tight, delicate, and difficult, conditions our crews encountered in the structure
Tight confines, delicate structures, and open excavated pits, made this jobsite one of the more challenging ones our team has faced.
Compact skidsteers were used to help attach helical piles to the excavators used to install them, but it took careful navigation to ensure no equipment ended up tumbling into a hole.
A single 9' x 10' opening in the brickwork between masonry columns provided our primary access to the interior. Our CAT 321, a 30 tonne excavator, was just able to squeeze its way through the opening.
What became instantly apparent was the overburden on site was teeming with construction debris, unmarked structures, pipes, and all the other surprises that come with such an old building. In fact there were so many obstacles it began to create problems with placement accuracy.
Our team immediately engaged Concorde and Crosier Kilgour & Partners to inform them about the issue and identify a solution. By working together with their teams, placement issues were swiftly resolved and the installation resumed.
However, it wasn't long before the building itself began to challenge our crews.
The first issue was that our 30 tonne excavator couldn't make it across the original vestibule floor. This wouldn't have been a problem, except that four of the helical piles required the crowd force of the larger excavator to ensure they met design loads.
Without the muscle of the larger machine, we couldn't guarantee the performance of those helical piles.
To overcome this roadblock, our crews carefully maneuvered the big excavator to the edge of the floor. Then, the arm of the excavator was used to gingerly install the helical piles through small 12" holes in the vestibule floor.
This ensured all piles could be installed to spec while minimizing restoration work to the floor in the vestibule.
The foundation designs also called for 24 helical piles to be installed underneath the original vestibule of the theater. However, the only access to the area was through a single elevator shaft opening. This made for some particularly tight confines as our crews installed piles to a design load of 24 kip [105 kN].
To install the helical piles in this exceptionally tight space, we enlisted the help of a spider crane from Mr. Boomtruck. Using the crane we could lower a compact Kubota U-17 mini excavator and palettes of helical piles into the basement through the elevator shaft.
Thankfully, our installers aren't afraid of a tight squeeze and were able to successfully install every helical pile to spec.
In total, it took our dedicated install crews just 24 days to install all 141 helical piles in this unique and demanding project.
With very few changes to the initial design and zero notable delays, the impossible foundation installation was complete.
Thanks to the tireless efforts of the professionals at Concord Projects, Crosier Kilgour & Partners, Wood PLC, SMP Services, and our team at VersaPile, this century-old building received a new lease on life.
Other foundation solutions for this project would have been too expensive, too dangerous, or too difficult to install. In fact, without a helical pile solution it's very possible this project may not have happened.
This project perfectly illustrates why helical piles are such a revolutionary foundation solution (that's nearly 200 years old). No matter the conditions, helical piles offer unrivalled versatility for commercial and industrial projects. From heritage buildings to transmission and distribution construction, odds are excellent there's a helical pile solution for you.
If you're curious about how you can use helical pile foundations in your next industrial or commercial construction project, scroll down to get in touch with our foundation team.
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