Auger Cast Piles

Under the right conditions, auger cast piles, also commonly called Auger cast-in-place (ACIP) piles or Continuous Flight Auger (CFA) piles, offer a number of scheduling and economic advantages over other deep foundation options. Installation is rapid and vibration-free.

Auger cast piles should be considered where speed of installation is important, a large number of piles are required, and access is unrestricted. Auger cast piles are typically installed in groups, similar to driven piles, and tied into a pile cap. Each pile is typically 12 to 18 inches in diameter and capable of carrying loads ranging from 10 to 150 tons. Depth of installation can be up to 100 ft. Decades of combined auger cast installation experience by our specialists, puts Moretrench in the forefront of North America’s auger cast contractors.

Installation

Piles are constructed by rotating a hollow stem auger into the ground in a single continuous motion. As the auger advances to design depth, the flights on the auger are filled with soil which provides lateral support and maintains hole stability. Once design depth is reached, pumping of high strength concrete through the hollow stem of the auger begins immediately. The auger is initially lifted a short distance to allow the hollow stem cap to be expelled by the pumping pressure and continuous grout flow to begin. The auger is then lowered again to design depth and controlled pumping continues as the auger is simultaneously slowly withdrawn. Since the process is continuous throughout auger advance and withdrawal, providing the required wall stability for the full length of hole, no casing is necessary. If required, reinforcing steel can be added while the grout is still fluid.

Applications

  • New building foundations
  • Retaining walls
  • Tank foundations
  • Sewer foundations

Advantages & Limitations

  • Speed of installation
  • Minimal noise and vibration
  • Very economic where large numbers of piles are required
  • Casing not required
  • Collection and disposal of soils can be an issue on contaminated sites or where there is limited handling room.
  • Soils containing boulders, underground obstructions, or highly variable ground conditions can be problematic.

Drilled Displacement Piles (DDP)

Drilled Displacement Piles (DDP) offer similar installation, scheduling and economic advantages to CFA piles. However, since CFA piling is a replacement technique, spoil is generated. The drilled displacement method, as the name implies, pushes the soil laterally rather than raising it to the surface therefore spoil generation is limited and disposal is not a major consideration. This can be advantageous where contaminated soils are present. Lateral displacement also has the effect of providing a degree of ground improvement around the piles which can improve bearing capacity. Drilled displacement piles are most effective in sandy soils where ground improvement can be realized, where limiting spoil removal is desirable, or where vibratory pile driving techniques are precluded.