Using Data to Build A Better Helical Pile Foundation

December 3, 2021

Would you drive a car that hasn't been crash tested?

What about flying in a plane that hasn't been flight tested?

Testing limits has given us a safer world. It helped design seatbelts, airbags, and autopilots. A world without testing would be chaotic and dangerous.

What about the foundation under your feet?

Like cars and planes, helical foundations are subject to intensive testing. These tests have let us build safer, stronger, more efficient foundations.

But, how?

It's time for a quick guide to what load testing is, how it works, and why it can give your commercial project a better foundation.

A Primer on Load Testing

Load testing is a way of measuring a helical pile's resistance to compressive, shear, or tension forces.

The concept of load testing a helical pile goes all the way back to their first recorded use in 1838.

In those days, they would secure a platform on top the pile and load it with stones. An engineer would check for pile creep using a measuring rod. Crude by our standards, but it proved reliable enough for the structures of the era.

Today, we command infinitely more control and precision in our load testing.

(Image: No more wooden platforms with stones needed today, now we can test piles in any location with a variety of test rigs and methods.)

Loaded Decisions

When, where, and how a pile is intended to be used will affect which load test is used. Helical piles that support guy wires are tested differently than steel beam supports, for example.

It's the job of the engineer to select the appropriate load test. They'll study the foundation, soil reports, and other data to choose the right test and methodology.

Today, for the sake of brevity, we'll look at a common load test - the axial compression test.

Abusing a Helical Pile

Axial compression testing determines the compressive (downwards) force a helical pile can resist. Since most helical foundations support compressive loads, this is a commonly-used load test.

A majority of helical pile companies run their axial compression tests according to the standard ASTM D1143. The ASTM has refined load testing on helical piles for several decades. The process I describe here is a (grossly) paraphrased version of their standards.

Equipment

(Image: One of the axial compression test rigs we have used at VersaPile to perform performance and safety tests on our helical piles. Here you can see the hydraulic jack applies force to a steel beam that's anchored to the pile. Gauges on top the jack measure creep - one of the many datapoints we collect during a load test.)

An axial compression test rig generally includes the following components:

  • Hydraulic jack to apply downwards pressure
  • Steel frame to support jack
  • Temporary piles to support test rig
  • Sensors and gauges to measure results

To ensure only axial force is applied to the pile, the test rig is carefully aligned to the pile top. Once everything has been checked (and re-checked) it's time to turn up the pressure.

Testing

The test rig applies force in varying intensity and duration. How much force is applied and for how long is determined by the project requirements, site conditions, regulatory requirements, and other factors.

(Image: Load testing can be carried out by a variety of setups and equipment. In this example, we used our heavy-duty truck with crane arm to apply the compressive force.)

During the test, heaps of performance data is collected by various sensors. This data is collected and assessed by a qualified engineer. And it's inside this data where you'll find the insights that help you build efficient, fast, high-performance foundations.

The Power of Load Testing

Usually, the primary goal of a load test is to confirm the helical pile foundation can support the weight it needs to. Safety, performance, and longevity are always our key considerations when load testing helical piles.

(Image: This rig is performing a tension test to see how much tension (upwards or lifting) force the pile can resist.)

But the data we collect can reveal a lot more than just the performance of a helical pile.

A trained engineer can use helical pile load testing data to leverage a wide range of benefits, including:

  • Value engineer a more efficient foundation
  • Assess specific capacity-to-torque correlations for the site
  • Confirm ultimate pile capacity - especially important in variable soil
  • Improve safety factors (on approval)
  • Identify changes in the composition of the soil
  • Create site-specific installation criteria
  • Test specific piles of concern to confirm capacity
  • Secure confidence in the foundation's performance
  • And much more

Why Load Testing Matters

Load testing helical piles lets us build smarter, data-driven foundations. No guesswork, no gut feelings. It's one of the (many) reasons helical pile foundations are seeing increasing use in commercial projects.

After all, if you can't measure something then how can you improve it?

A well-executed load test gives you deep insights into your foundation and the soil beneath it. More than that, it equips helical pile companies (like us) with the knowledge we need to build the most efficient foundation for your project.

Quality data is the lifeblood of modern construction, and helical pile foundations are no different. The more data we can collect, the better we can build.

Curious to know more about load testing, or just have some questions about helical piles? Click here to get in touch with our team of friendly foundation experts. We'd love to offer our help!

 


View More News