Keller reaches record depths in US pile installation

Global engineering company Keller is installing over 400 continuous flight auger (CFA) piles, reaching depths of up to 61m (200ft), at the St Regis development in Sunny Isles Beach, Florida, US, the deepest full-length reinforced piles the company has installed.

Once complete, St. Regis will be the tallest development in the city, featuring two towers over 18m (60ft) high with nearly 400 luxury residences on the beachfront. Keller has extensive experience in the area, having worked on nearly every building development there, and, says the company, the piling development will allow its clients to construct taller, slimmer buildings more cost-effectively.

The site presents challenges due to soft limestone layers that can complicate settlement. The St. Regis project will also feature the deepest cantilever coastal basement excavation, extending up to 14m (45ft). Significant engineering efforts are required to manage the soil and water pressures at this depth.

“Keller has a long track record with our clients at Coastal Construction, as well as the developers Fortune International Group and Château Group,” said José Delgado, vice president at Keller. “Our early involvement through a design-assist build has been crucial to the successful delivery of this project.”

With rising demand for housing, tall buildings require deeper foundations. Keller has developed new equipment to facilitate the installation of deeper piles. These deeper piles can save clients between 30% to 40% in costs and reduce project schedules by four to five months compared to other methods.

Installing such large piles poses specific challenges. Unlike sectional piles, continuous drilling is needed, followed by pumping grout back to the surface. This process requires strict quality control to ensure the grout is consistent.

The project also features a 10,000 square metre (108,000 square feet) double-level basement, which must be both safe and watertight for the pile cap and basement wall construction. Keller used bottom soil mixing and reinforced cantilever deep walls to avoid the need for bracing that could compromise waterproofing. Large diameter tubular soil mixing walls support the structure, with temporary tiebacks used to maintain stability during construction.

Work on the piles, which range from 27m (90ft) to 61m (200ft) deep, began in August. Once complete, Keller will proceed with excavation, hauling, disposal, pile cutting, and dewatering.

“As with every Keller project, quality control and safety are our top priorities,” Delgado added. The site is active, with over 50 crew members, three soil mix rigs, two cranes, and various other machinery operating near valuable neighbouring buildings.