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There’s a couple different types of “myths” in the world. The first is the cool kind, like the stories about Paul Bunyan or the Jersey Devil. I get to see and hear a lot of different and interesting folk tales in my travels across the United States.
Unfortunately there’s another type of myth out there. This type of myth isn’t cool at all, but I do hear it frequently all across this great country.
“Oh no,” I hear you thinking, “John’s about to go off on a weird tangent again and make it about helical piers.”
You know what? You’re 100% right. Because today I’m going to uncover a false myth that surrounds helical piers. Read close, because this myth could even cost your project valuable money and time…
Helical piers aren’t designed for heavy-duty, high-capacity applications.
I’ll be clear: this myth is completely false.
Not only are helical pier foundations able to support immense weight, they were designed from their very invention to uphold big axial loads. Far from being a “deck and fence” foundation helical piers are a tougher-than-nails, high-capacity, deep foundation that’s perfect for heavy commercial and industrial use.
But, how much weight can a helical pier actually hold?
Before we can talk about how much a weight helical pier can support, you need to understand how a helical pier works. I’ve heard people describe helical piers as basically a “supersized screw“, but that’s not an accurate picture. A helical pier operates on completely different principles.
To understand how a helical pier works, you have to understand how they’re built:
The pier shaft makes up the “body” of the helical pier, and is what all other components attach to.
Like everything on a helical pier, the shaft is made from steel. Depending on the application it can be manufactured from hollow round or square pipe, or solid square/round bar.
At the bottom of the pier is the lead section. It’s the first part of the pier to go in the ground and has a “pilot point” along with one (or more) helix plates.
The pilot point is usually cut at a 45 degree angle to make installation easier. Other types of pilot points, like carbide tips, can be used depending on the site requirements.
One of the benefits of helical piers is that they’re manufactured in sections. So, if you need to go 75ft into the ground, you can add 25ft extensions until your desired depth is reached. More on couplers below.
That means helical piers can be quickly adapted on-site to deal with unexpected or challenging soil conditions.
Let’s use an example. We’ll say that during the design phase, your foundation contractors received a geotechnical report indicating supportive soil at about 45 feet. On install day, the install crew finds the soil underneath a couple piers is still mush at 45 feet. In this case, extensions can be added until the pier hits supportive soil.
A coupler connects pier extensions together. Couplers come in a variety of designs. They may be threaded, bolted, or welded depending on the project.
A helix plate (pl. helices) is manufactured from a steel plate, cold-stamped into a helical shape and welded to the pier shaft. The helix plate is the “secret sauce” of a helical pier and is responsible for providing much of the support.
Helices are attached to the shaft in such a way so that they follow the same path through the soil. This minimizes soil disturbance and can increase the pier’s capacity.
Helices follow a defined pitch, typically 3”, regardless of the diameter of the plate. This defined pitch makes it a true helical pier. How many helices are used depends on the project requirements. If you need a high-capacity foundation in poor soil, your helical piers may have as many as 4 or more helices.
The pier cap helps transition the pier sitting in the ground to whatever structure or project it needs to support. These caps can be off-the-shelf components or custom-made to suit the exact project demands.
One of the reasons so many companies use helical piers these days is because of the versatility of pier caps. No matter what you need a foundation to support, there’s a pier cap that’ll do the job.
All those components are crucial to the performance, versatility, and strength of a helical pier. But, there is one component that’s responsible for most of a helical pier’s capacity.
The mighty helix plate.
It’s the unique properties of the helix plate that allow helical piers to support much more weight then their look suggests. A properly-manufactured helix plate will have parallel leading and trailing edges, as well as a specific pitch (usually 3 inches).
The helix plate provides a wide area to disperse the load of the structure above ground. It’s the resistance of the soil on the helix plate that provides axial and tension capacity.
(Soil friction on the pier’s shaft also plays a role in determining the ultimate capacity of a helical pier, though not as much as the helix plate.)
To recap: it’s the resistance of the soil on the helices that provides much of a helical pier’s capacity.
Alright, to the core of our question. Before I give you an answer, though, a quick caveat:
The ultimate capacity of a helical pier foundation depends on a range of factors that include the foundation’s design and properties of the soil. To get a reliable helical pier capacity for your project, talk to one of our helical foundation experts to assess your requirements and site conditions.
Enough caveats, it’s time to answer the big question with an example from one of our own projects.
An oil & gas facility in Texas was expanding their facility with a new slug catcher. It was a heavy beast, with an ultimate compressive load over 1 million pounds.
The unique design of helical piers means they can be installed in soil conditions and locations that other deep foundations simply can’t
Concrete was considered, but the soils in West Texas are generally dry, tough, and full of gravel. Excavation can be a big challenge and our customer didn't want the hassle of removing spoils. Plus, the location of the facility made concrete costly to source and slow to install.
Driven piers were also considered, but their cost and the potential for vibrations eliminated that solution as well.
Our engineers designed a foundation consisting of 7″ diameter and 8.625″ diameter helical piers, installed in a battered configuration for axial and lateral support. The piers were welded to steel I-beams to tie everything together.
“But John!” I hear you shout, “1 million pounds over 148 helical piers is only 6,700 pounds of capacity per pier. What gives?”
Designing a helical pier foundation is about much more than the per-pier capacity. It's about the type of structure and loads you're supporting. The foundation of a slug catcher has intense and complex loads exerted on it. Helical piers are exceptional at resisting those loads because of their unique design and versatility.
However, if you're wondering how much weight a single helical pier could hold...
A few years ago, we installed beefy 14″ diameter helical piers for a compressor station. On that job, our helical piers comfortably sustained an ultimate load of 400,000lbs per pier. They could have easily gone even higher, but 400,000lbs was the specified capacity and so the test stopped there.
What I’m saying is the load capacity of your individual helical piers is not a limiting factor for your foundation.
Helical pier foundations are just as capable, sometimes even more so, than comparable cast-in-place or driven concrete piers. The hefty axial capacity of helical piers makes them great for projects like:
● Battery Energy Storage Systems (BESS)● Renewable energy projects (solar installation, wind turbines)● Oil and gas applications (pipelines, equipment support)● Power transmission lines and communication towers
The question isn’t what can helical piers support, it’s what can’t they support
If someone tells you helical piers can’t be used in a high-capacity application, they (frankly) don’t know what the heck they’re talking about.
Helical piers were originally invented almost two hundred years ago to support high axial loads in very weak soil. Decades of intensive engineering, testing, and study, have turned helical piers into proven high-capacity foundations with the data to back them up.
Put your project on a stronger, faster, more economical foundation, scroll down to get in touch with our foundation experts at S&B Helical. Whether you need to support 100,000lbs or 1,000,000lbs, we'll help you uncover a fast and efficient solution.
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