Keller will participate in a Miami project in which, for the first time in 50 years, auger cast piles will be utilized.
The $800 million Signature Bridge is part of a major regeneration plan in Miami and is handled by the Florida Department of Transport (FDOT).
Auger cast piles or continuous flight auger piles are cast-in-place piles, using a hollow stem auger with continuous flights. FDOT’s preferred foundation method of precast piles but they wouldn’t have enough load capacity while drilled shafts would take too long. Therefore, they needed a new solution.
Experience and expertise
Keller has successfully used auger cast piles for around 90 percent of high-rise towers in the area, achieving several world records along the way, helped convince the consulting engineers to meet with Keller and develop an auger cast pile design solution. That solution was then presented by Keller to FDOT and general contractor (Archer Western-de Moya joint venture), who green-lit the project.
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. “Usually, we’d measure lateral pile movement at the surface, but for this project, Keller wanted to provide a greater level of reassurance. So that’s why we installed the instruments inside the pile casing to monitor movement for the top 60 feet of the pile, with sensors spaced every 0.5 meters. Data was collected every minute during the test and was made accessible to the client via a dedicated website for easy access and review while the test was ongoing," Gabriel, stated.
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 (76 to 91 centimeters), up to depths of 134ft (40,8 meters).
The project is moving well despite its challenges. “We’re one of the few companies capable of installing piles to such depths with full-length reinforcing. 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,” Andres Baquerizo, Keller Vice-President – Special Projects, explains.
Opening up a new market
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.
“The fact that we’ve been able to convince FDOT not only to accept large auger cast piles but also to use low-headroom piles, shows they have complete trust in us. We’re very aware of that, we’ve got an amazing team and superintendent working on the project and we won’t let the client down,” Andres added.
Since FDOT commissions more new projects with auger cast piles, a new market is opening up that could see more opportunities for Keller to support state infrastructure.
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