Continuous Flight Auger Piles Are the Right Solution for 5600 S Pedestrian Bridge

CHANGE

The Progressive Design-Build project team, including geotechnical and structures consultants, proposed using Continuous Flight Auger (CFA) piles for the bridge foundations. This was the first use of CFA piles on a UDOT project and required extra documentation and testing to meet approval.

CFA piles are created with the use of a hollow-tipped auger that maintains the stability of the excavation or hole. Once the hole is completed, the auger is withdrawn while a grout/concrete mixture is simultaneously pumped into the hole forming a pile. By pumping as the augers are withdrawn, the hole stability is maintained first with the casing and second with the grout mixture. Reinforcing steel cages are then placed while the grout is still wet. 

Once the grout has set, there is no change to design, service life, or maintenance compared with alternative foundation systems. The CFA piles were tested using thermal integrity profiling methods and an adapted dynamic test method using a specialty frame and 49,000 lbs drop weight to demonstrate pile integrity and resistances.

RESULT

The CFA piles provided multiple advantages for this project:

• Minimal impact to adjacent property owners (within 20 feet of homes).

• No impact to adjacent sidewalks, accessways, or school walking routes.

• The work was completed safely without any incidents.

• The foundation was constructed more quickly than using other methods (in total 36 CFA piles installed, and select piles tested, in about a week).

• Saved money and demonstrated proposed CFA piles methods worked successfully.

• If CFA piles were not used, multiple utilities would have been impacted and potentially required relocation.