The project team explored several piling options, including hammered timber piles, drilled micropiles, concrete pre-stressed piling, auger cast, and helical piles.
Driven piles were economically viable but were eliminated from consideration due to access issues and noise/vibration concerns. Drilled micropiles and auger-cast piles both presented low-noise and low-vibration answers but were too expensive and generated significant spoils.
Helical foundation piling, was both an attractive selection due to ease-of-access, subtle vibration, and comparatively affordable cost. The team conclusively selected helical piles as the most appropriate and cost-effective piling preference for the project. It tendered low-noise and low-vibration where the driven piles could not offer low-noise and excessive vibration would be an issue.
The final pile engineering was performed by Reuben Clarson Consulting and featured a galvanized 49 ksi steel pipe section manufactured by “Chance”. The piles consisted of a 2 7⁄8-inch-diameter, 0.203-inch-thick shaft with triple-helix (8-inch/10-inch/12-inch) lead sections. The piles were designed to derive end-bearing capacity in the dense soil layer above the fractured rock layer.
Before the installation of production piles, the General Contractor, Fowler Construction and Development, pre-excavated pile locations to eliminate potential obstacles, including piling and concrete blocks. Pre-excavation proved to be worthwhile, as all 58 piles were successfully installed at their planned locations (Two Pilings were relocated due to debris). Upon termination, all helical piles were cut to their required elevation, and the interior portion of the pipe shaft was pumped with concrete grout to provide additional corrosion defense and pile rigidity. All helical piles were rotated into position in 5 days, which included mobilization. Pile production included a full-time Quality Control person to oversee pile testing and installation. Pile monitoring was performed by Velocity Engineering of Fort Myers, Florida.
The helical piles were installed by Coastal Foundation Solutions (CFS), a Certified Installer of “CHANCE” Helical Foundations Systems.
Sixty (60) “CHANCE” 2 7⁄8-inch-diameter, 0.203-inch-thick shaft with triple-helix (8-inch/10-inch/12-inch) lead sections were installed. The foundation helicals were positioned with a Komatsu 88 excavator powered by a 10K Pro-Dig hydraulic drive head. CHS advanced the foundation anchors to lengths on the order of 15 to 21 feet to achieve final installation torques. The ultimate required load bearing in compression was 20 KPS. Seventy-five (75) “CHANCE” (RS2875.203) round helical extensions were supplemented to lead sections. This provided adequate capacity in the existing soils. Additionally, a portion of the helical foundation pilings were affixed with a galvanized 7’ by 7” termination cap.