Our Unique Polyethylene Green Sleeve

Let’s look at one feature that makes Techno Metal Post stand out from our competitors: Our high-density polyethylene green sleeve. It offers a unique benefit because of its design to reduce friction between the surrounding soil and the helical pile.

For over 30 years now, Techno Metal Post has promoted using the green sleeve during the installation of helical piles, particularly for those installed through a layer of soil subject to freeze/thaw cycles. When the ground freezes, it causes the soil to expand and push the ground surface upwards, resulting in frost heave. Expansive soil can also alternate between shrinking and swelling with seasonal changes in its moisture content.

Over time, we observed that using the green sleeve reduces the risk of piles lifting/heaving in winter and thus promotes their stability throughout the seasons.

During 2020, TMP undertook a process to characterize and quantify the positive effects related to the use of the green sleeve. A field load test campaign was completed in March 2022 by TMP and witnessed by a third-party laboratory. The objective was to validate the effectiveness of the green sleeve on our helical piles, models P1 to P5, for two different types of soil (granular and cohesive).

The test consisted of conducting pull-out load testing on pile shafts installed with and without a green sleeve. Based on the analysis of different results, the conclusion showed that friction can be reduced on average by 67% between the pile with a green sleeve and the frozen ground.

Important to note: Normally, helical piles are designed to be anchored in a stable layer of soil and installed below the frost line or zone of potentially swelling soil. Helices in a deeper soil layer resist uplift forces caused by frost or expansive soil. Adding insulation, especially when piles are installed under a concrete foundation, can also provide protection. That explains why some structures built with Techno Metal Posts have no sleeve.

However, for shallow applications of light loads, such as deck foundations, patios, or other residential structures, we recommend our high-density polyethylene green sleeve to reduce the effects of soil friction and expansive soil.

For those familiar with the installation of helical piles, the helix goes into the ground with ease until the minimum torque is reached. However, in some cases, the installer has to contend with some obstacles, making for a more challenging installation requiring some soil disturbance around the helix and pile itself.

Often observed with rocky soils, this shuffling, however minimal, can create a water infiltration point which reduces the helix's ability to regain vertical uplift force resistance. By winter, accumulated water has frozen, causing potential soil movement which increases the vertical friction force along the pile.

For such situations, Techno Metal Post's green sleeve plays an essential role: it acts as a barrier between the soil and the pile. The sleeve slides along the pile without compromising the stability of the pile.

The soil eventually and naturally reconsolidates with the seasons. This reduces infiltration while increasing the pile's capacity to withstand the vertical forces caused by the freeze. The need for a green sleeve is therefore essential for the first 2 to 3 years following installation.

Eventually over the years, the sleeve might gradually move upwards. Cutting off the excess with a utility knife will prevent excessive build-up on top of the pile as well as improving the aesthetic appearance.

In some cases, after several years, the sleeve may completely come off. By then, it won't be necessary. The soil will have completely reconsolidated around the pile, allowing it to absorb the vertical forces of the freezing conditions without it shifting.

Overall, adding the polyethylene green sleeve during a pile installation greatly reduces the risk of piles lifting/heaving in winter and allows the stability of your structure on a long-term basis.

Call your local dealer if you have questions, they will be happy to chat with you and take the time to explain the benefits of our technology. Click here to contact a dealer.