LRE Installs Helical Piles to Support New Walkway in Miami Beach, Florida
Challenge
Belle Towers is a luxury condominium on Belle Isle, an island located just east of the Miami Beach, Florida coastline. This eight-story tall waterfront structure was constructed in 1958 and has 46 condominiums. The outside walkway to the main lobby entrance consisted of a carport and valet booth with pathways to the main entrance around a koi pond. The walkway was a concrete slab-on-grade with a tile surface and had exhibited significant settlement, which resulted in areas with potential trip hazards. One concrete core was performed at the south area of the walkway slab which showed a 20-inch void directly below the slab that was believed to be the result of water erosion. One soil boring was advanced near the carport at the south end of the walkway to a depth of 25 feet. The soil profile at the boring location consisted of very loose to loose sand to a depth of 4 feet where a 2-foot layer of decomposed organics above a very loose silt and organics extending to a depth of 15 feet was observed. Loose silt was observed below the organic soils to a depth of 20 feet, where weathered limestone was encountered to the termination of boring. Groundwater was observed at a depth of 5.4 feet at the boring location. The proposed slab repair options included either filling the void with cementitious grout and cosmetic repair to the walkway surface or slab replacement and a deep foundation system to transfer the walkway loads to the deeper limestone formation.
Solution
Void filling was not considered a permanent solution given the thick layer of compressible soils that would continue to settle under the weight of the slab and void fill material. A more permanent solution consisting of removal and replacement of the slab with support from a deep foundation system was chosen. The scope of work also included renovations to the front lobby entrance and a new carport and valet booth. Helical piles were selected as the preferred deep foundation alternative for the walkway slab given the ability to work around tight access areas and underground utilities at the koi pond, the quick installation, and lower costs relative to other deep foundation alternatives. The new walkway design required 22 helical pile locations with service compression and tension loads of 18 kips and 9 kips, respectively. The Model HP288 (2.875-inch OD by 0.276-inch wall) hollow round shaft helical pile system with a 10”-12”-14”-14” helix plate configuration with new construction brackets was selected for the slab support. The helical piles were installed to depths of 22 to 47 feet after achieving a torque-correlated ultimate capacity of at least 2.5 times the service load. The 22 helical piles were installed over a period of 4 days.
Project Summary
Structural Engineer: Visioneering, Inc.
General Contractor: Complete Property Services
Geotechnical Engineer: Wingerter Laboratories, Inc.
Helical Pile Designer: FDN Engineering
Helical Pile Installer: LRE Foundation Repair
Product Installed: (22) Foundation Supportworks® Model 288 Helical Piles, Service Compression Loads of 18 kips, Service Tension Loads of 9 kips, Installed Depths of 22 to 47 feet.
