HELICAL ANCHOR AND EROSION GUARD SYSTEM INSTALLATIONPROJECT INFORMATION
In July of 2018, Coastal Foundation Solutions was contracted to install a series of helical anchors as well as install an erosion guard system at Gulf Harbor at Bonita Beach in beautiful Bonita Springs Florida. Gulf Harbor Condominium of Bonita Beach is an extraordinary gem presenting Island Living at its finest. The development is situated on the tranquil north end of Little Hickory Island with direct access to the Gulf of Mexico.
Amenities available at Gulf Harbor include, community swimming pool and spa, fishing pier and dedicated boat slips. In addition, there is a unique large boat house to moor two boats. The development has 180 lineal of seawall on Big Hickory Pass.
The development was experiencing settling of the pool deck and sporadic cracks in the concrete retaining wall. The seawall was also rotating out of alignment due to age of structure.
PROJECT CHALLENGES
Forge Engineering of Naples, Florida conducted a geotechnical investigation and suspected the cause of settlement to be the existing pool retaining wall was failing due to soil migration through the concrete seawall. In addition, investigation revealed that up to 95% of the tie-back anchor’s cross section was lost due to corrosion.
The pool pavers settled differentially up to 2 inches toward the south of pool and up to 3 inches in the north area of the swimming pool and spa. Sloping pavers and cracks in the exterior retaining wall were observed as a result of the settlement. The area had extremely limited access for even small equipment.
HELICAL PILE INSTALLATIONTHE SOLUTION
Coastal Foundation Solutions had to deploy our specialty equipment to proceed with this stabilization project. We launched our 26-foot aluminum barge from the condominium parking lot into Big Hickory Pass with a 75-ton crane. Next, our Kobelco mini-excavator was flown unto the barge to facilitate installation of helical compression piles and helical tie-back anchors.
The engineer designed a system of hydraulically-rotated helical piling to permanently stabilize a new retaining wall and spread footing. In addition, the existing concrete seawall required supplementary helical anchors.
The compression piers were advanced to depths of approximately 17-21 feet to bear below the organic material and achieve a design working load of 10 kips per pier. These piling would support the new spread footing for the retaining wall. A hydraulic drive rotated the supplementary 6”-6”-6” triple-helix lead section, which was installed through a six-inch diameter cavity opening. Coastal Foundation Solutions utilized combinations of specialized concrete core bits to gain access through existing 6” thick vertical seawall.
The cavity was filled with a 6” polystyrene foam plug and a H.D.E.P. membrane to prevent soil loss after helical anchor installation.
Coastal Foundation Solutions was also tasked with eliminating soil migration through the existing seawall seams. This methodology entailed scrapping the marine organisms off the concrete seawall and seams. We then installed a backer rod that has a closed cell exterior into the seams which is permeable to allow water to escape but contain soil properties. A ¼” P.V.C. panel was the attached to the wall and fastened with ¼” 316 Stainless Steel anchors.
The project entailed utilization of thirty (30) helical anchors to be installed in tension and compression.
PRODUCTS
Helical piles were installed by Coastal Foundation Solutions (CFS), a Certified Installer of Seawall Savers and Chance Helical Foundations Systems.
COMPRESSION PILES
Ten (10) CHANCE 2 7/8” round shaft helical piles with an 8”-10” 12” triple-helix lead section were installed with a 6K Eskridge drive head. The Kobelco excavator progressed the extensions to lengths on the order of 17-21 feet to achieve final installation torques. The ultimate capacities of at least twice the design working tension load of 10 kips
Twenty (20) “CHANCE” (RS2875.203) round helical extensions were installed to corresponding capacities to secure tension load of 10 kips.
The helical foundation pilings were affixed with a galvanized 7’ by 7” termination cap.
TENSION PILES
Twenty (20) Seawall Saver SS150 (1.5-inch square bar) helical piles with a 6”- 6”- 6” triple-helix lead section were installed with a 6K Eskridge hydraulic drive head. The mini excavator rotated the square extensions to lengths on the order of 15 to 21 feet to achieve final installation torques. The ultimate capacities of at least twice the design working tension load of 12 kips
Thirty-one (31) “Seawall Saver” square shaft helical extensions were installed to corresponding capacities.
The helical tension pilings were affixed with a 1” galvanized rod, that is attached to a galvanized 7” by 18” structural steel “C” channel.
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