Keller is taking a lead role on the first Florida Department of Transport project for half a century to use auger cast piles. We spoke to the project team to find out how it’s going.
It’s a high-profile project for the Florida Department of Transport (FDOT) and one they’re keen to get absolutely right. But when early tests showed that the FDOT’s preferred foundation method of precast piles wouldn’t have enough load capacity and that drilled shafts would take too long, they needed a new solution.
Experience and expertise
“The FDOT had a very bad experience with auger cast piles about 50 years ago, and ever since they’ve been reluctant to use them again,” explains Andres Baquerizo, Keller Vice-President – Special Projects. “But over the last few years, as part of my role on the National Committee of the Deep Foundation Institute, we’ve been promoting advances in auger cast pile technology and explaining how this is now a technique you can genuinely trust.”
Rigorous testing
After intense negotiation, Keller was awarded the contract and started on site in September 2019. Work began by carrying out a rigorous regime of test piles, with support from affiliate GEO-Instruments and specifically Area Manager Lee Gabriel.
Making progress
Over the next couple of years, Keller will work in phases to install more than 2,000 auger cast piles, with diameters of 30 and 36 inches, up to depths of 134ft.
“We’re one of the few companies capable of installing piles to such depths with full-length reinforcing,” adds Andres. “Traditionally, the FDOT has specified fixed-lead rigs on site because of a belief that you always need pull-down force to drill to the specified depths. The fixed-lead rigs have drilling depth limitations that prevented their use on parts of this project. We were able to prove that our design-build equipment (leads, augers, drill bits, power units, etc) were specifically designed for such purpose and had been successful in thousands of projects.”
Opening up a new market
The other main challenge has been logistics, as Nick explains: “It’s a bridge, so we’re working on a series of small sites along a mile-long stretch in a built-up area. We’re having to move regularly, which requires careful planning. We also start work at around 3 am before the traffic gets too busy, and finish in the early afternoon.”
Because of an existing bridge nearby, Keller is recommending low-headroom piles in some areas. This will allow the team to install foundations without the need to first demolish the original bridge, saving months on the schedule and minimizing traffic disruption.