Helical Piles

Helical piles are often considered the new kid on the block and the local engineering network might not have received much training or education on the design, installation or general engineering principles specific to helical piles. However, helical piles have nearly two centuries of historical use. Invented in the 1830’s in the UK by Alexander Mitchell, helical piles were first engineered to support marine structures such as lighthouses and boat moorings in the ocean.

In the late 1800’s and early 1900’s hundreds of lighthouses were constructed along the eastern seaboard of North America on helical piles – remarkably, some of them still stand today.

There are few projects where the soil conditions would prove more challenging than building in an ocean. Recognizing that helical piles were performing well in such a challenging environment, the engineering community in the late 1800’s began to leverage helical piles mainland.

In the early 1900’s nearly all deep foundation options required a lot of labour to install and helical piles were no exception. Cap stands were constructed and powered by many men or animals who would turn in circles to advance helical piles. By 1920 a new and slick steam powered pile driver was available and made it very efficient, for the era, to lift and drop heavy weights to pound timber into the ground. The result was that helical piles which were growing in popularity to this point, fell out of favour and were replaced by easier pile driving methods.

A variation of helical piles did emerge and is known today as a ground anchor. The utility sector was expanding rapidly and required lateral support of transmission poles with guywires secured by anchors. Helical piles were well known for their ability to support compressive and tensile loads but, as mentioned above, they were laboursome to install. The utility sector found that if they greatly increased the pitch of the helical, they became much easier to install. The ability of a ground anchor vs a helical pile to support compressive loads was greatly diminished as the engineering community found ground anchors were prone to self-advancement under compression.

After several decades of declining usage, helical piles once again emerged as a viable option as hydraulics and planetary gears and high torque drives came to market. Slowly, helical piles emerged back into the deep foundation market.