What if We Built an Indestructible Helical Pile?

November 5, 2021

The other day, my kids wanted to watch one of the Marvel superhero movies. In one scene, the character Thor thundered his mighty hammer into Captain America's shield. The shield didn't break. Clearly, it wasn't made with your standard cold-rolled steel.

While that scene was standard stuff for a flashy superhero movie, it got me thinking about an indestructible helical pile. Specifically, I remembered a recent advertisement from a helical pile manufacturer. In it, they claimed their piles had more capacity because they were built with "higher grade" steel.

On the surface, that's a reasonable claim. After all, using a stronger material should increase the capacity of the helical pile... right?

Not quite.

You see, using a stronger material for a helical pile doesn't mean it will support more weight. To prove it, let's imagine we could build a helical pile from the strongest material in the universe.

A Heroic Helical Pile

As the story goes, Captain America's shield was made from a fictional element called "vibranium". It's supposed to be virtually indestructible, so it makes a perfect material for a hero's shield.

But could it be the perfect material for a helical pile? Let's say we have an indestructible vibranium helical pile manufactured and ready to install. How much weight could it support?

Before we can answer that, we need to understand how a helical pile supports a structure.

The Helix - A Helical Pile's Superpower

Helical piles have several unique and, in my opinion, fascinating design elements. I don't have space to cover all those here, but that's okay. Today we're interested in the helix plates (pl. helices), a helical pile component that holds to answer to our question.

(Image: Diagram of a helical pile with labeled components - note the helix plate at the left-hand side [what would be the bottom of the pile])

Helix plates are made by taking steel and stamping it into a spiral shape. This shape allows the helical pile turn into the ground and provides load resistance. As the helical pile turns into the ground, we monitor the torque it takes to install. As the soil exerts more force on the pile, it reads as increased torque. To make a complex principle (grossly) simple, more torque equals more capacity.

But, why?

The Soil is the Key

The pile shaft is narrow in comparison to the helix plate. This means applied loads focus on that plate (or plates). The large surface area of the plate anchors against the soil. This provides the bearing needed to resist loads.

(Image: A high-capacity [210,000lbs] helical pile for a 5-storey mixed use building. The 32" diameter helix plate offers immense support due to its wide surface area.)

More simply put, the force of the soil on the helix plate(s) give the pile its capacity. Which brings us to our question: what if we made a helical pile from Captain America's shield?

Truth, Not as Strange as Fiction

An indestructible vibranium helical pile would be pretty cool. Sadly, it wouldn't offer significantly more capacity than a steel helical pile. Plus, I imagine finding a welder to work with it would be a challenge.

The material of a helical pile doesn't determine ultimate capacity. The soil around the helix plate(s) will decide that. As such, the limiting factor isn't the helical pile material but the soil. That doesn't mean the pile material is unimportant. High-quality steel should be the default, and already is amongst reputable manufacturers.

Don't trust those who claim to have high capacity piles because they use "high grade" steel. That's marketing smoke and mirrors.
Invest in expert contractors and solid engineering. That's the best way to get a quality helical pile foundation.

Have some questions about helical pile caps, or anything else related to foundations? Why not click here to get in touch with our friendly experts, we'd love to help you find the right answers.

 

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