One of the reasons why screw piles are such a popular choice of foundation is that they are so quick and easy to install. But that doesn’t mean that precautions don’t need to be taken. On bigger commercial projects tension testing can provide crucial data needed for project success. So, what do you need to know?
Screw Piles and Tension Testing
What is tension testing?
Tension in screw piles refers to the upwards pressure that the pile is able to resist. So, imagine you have a permanent marquee erected, and it’s tethered in place via screw piles. With every gust of wind, the upwards pressure would be putting strain on the screw piles, trying to pull them out. Tension testing is a way of measuring how much upward pressure it takes to displace your piles. In other words, what it would take to pull your screw piles out of the ground.
How do you perform screw pile tension tests?
There are a couple of different methods for conducting screw pile tension testing. In most cases, piles are installed with strain gauges or extensometers. You will then follow these steps:
- Choose which piles to test – at least three should be selected, depending upon the size of the build. And make sure they are properly installed with the relevant equipment in place.
- Clear the area around the piles.
- Install and calibrate any relevant equipment, including measurement instruments, such as displacement transducers or strain gauges.
- Use a winch or hydraulic jack to gradually apply upwards pressure to the selected pile. Incrementally increase the upwards pressure, while monitoring the pile’s response, recording your data as you go. It is essential to ensure that the force applied to the pile is absolutely vertical in order to acquire accurate results and to avoid damaging the pile.
- Measure movement and settlement in the soil within the vicinity of the screw pile.
- Refer all collected data to an engineer for assessment.
An axial rig and ‘reaction piles’ can also be used for this process.
Why should you perform screw pile tension testing?
The primary reason for any form of screw pile testing, whether lateral load, compression, or torque, is safety. Essentially, to assess whether the screw-pile design is adequate for, and exceeds by several factors of safety, the application. In order for your structure, be it house, extension, garden room, pier, or solar array – to be durable and safe, you must ensure that its foundations are secure. When screw piles are poorly installed, they will ultimately impact the overall viability of the structure and project as a whole. So, on large scale projects with lots piles or structures or over an extensive site, testing for tension is often recommended.
Tension testing screw piles may add a small amount of time to your project. But it is time well spent. By ensuring that your piles can withstand upwards pressure, you are providing the best possible foundations for your structure. Helping to enhance its longevity and reducing the need for possible remedial care at a later date.
Contact UK Helix to discuss your screw pile needs.