Helical Piles
Helical piles are deep foundation elements that are used to support new foundations or underpin existing foundations. They generate no vibrations and can be installed with only 6 feet of overhead space and in other limited-access situations. The pile shafts are made of galvanized steel and are installed in short sections, each about 5- to 7-feet-long. Each pile consists of a lead helical section with welded screw-like bearing plates; subsequent straight-shaft sections are mechanically-fastened to the lead section as it is advanced into the ground. The piles are installed with a skid-steer or an excavator equipped with a high-power torque head, which is calibrated to directly correlate torque resistance with pile capacity. Helical piles can also be installed with hand-held torque motors for locations that are not accessible with a skid-steer or small excavator.
Helical piles can function as end-bearing or side-friction elements. For an end-bearing pile, the lead section is advanced through the unsuitable soil layers and into an underlying bearing stratum until a predetermined design torque value is achieved. For a side-friction pile, “digger plates” are added between each pile section in order to create annular space around the steel shaft, and the annulus is filled with grout as the pile is advanced into the ground. This process creates a grouted bond with the surrounding soil, resulting in a helical micropile. Similar to a Drilled Micropile, a side friction helical micropile is installed to a predetermined design depth.
Helical piles are ideally suited for foundation support or underpinning requiring low to moderate pile capacity. Alternative foundation options including Ductile Iron Piles or Drilled Micropiles may provide greater design efficiency and cost-savings by affording higher pile working capacity.
Helical piles can also be used as anchors or Tiebacks.
