SEAWALL STABILIZATION USING HELICAL ANCHORSPROJECT INFORMATION
Town & River is an exceptional waterfront neighborhood situated in South Fort Myers, off McGregor Blvd with fantastic waterfront views. Town & River features single family homes and waterfront condominiums, many of which are set on extensive canals that offer direct access to the Gulf of Mexico. For the avid boater, this area is truly one of the exceptional ”Deep Water” canal systems in Fort Myers
HELICAL TIEBACKS FOR A FORT MYERS NEIGHBORHOOD SEAWALL
Numerous out dated homes in Town and River have been renovated or bulldozed for new home construction because of magnificent waterfront panoramic views. The owner had elected to demolish the existing home and construct an exquisite new family home. He contracted with a local marine contractor who replaced his aging seawall with a new concrete seawall. Unfortunately, the new seawall failed after five (5) months due to a litany of problems. The primary contribution of wall failure was due to severe incompetent soil conditions and inadequate seawall panel penetration into substrate.
The owner contacted Hans Wilson and Associates to design a new seawall with proper panel penetrations and tie-back system. The new wall would be a challenge due to the proximity of the new swimming pool and retaining wall to seawall. The outside entertainment area would be situated within six (6) foot of the new vinyl seawall.
PROJECT CHALLENGES
Benton and Sons were contracted to install a new vinyl seawall with a commercial engineered concrete cap. The conflict arose when it was revealed that the new home would have a swimming pool installed within eight (8) foot of the new seawall. This would be a challenge to the marine contractor to install conventional tie-back and concrete dead-men. The depth of the dead-men would be below the low tide water line. This would entail deep excavations utilizing trench boxes to protect workers from soil collapse.
Consequently, traditional concrete deadman and tie-back reinforcing rods could not be installed due to depth of proposed swimming pool depth. The engineer and contractor elected to incorporate a helical tie-back anchor system to sustain new seawall alignment.
HELICAL TIEBACK ANCHOR INSTALLATIONTHE SOLUTION
Coastal Foundation Solutions was contacted to provide additional engineering and expertise for the project. We determined that our helical pile tieback anchor system would have to be securely drilled into the subsurface soil to reinforce the proposed vinyl seawall.
In addition, the soil borings revealed poor soils within the range of helical anchor embedment. Consequently, a refined helical tieback anchor system would be required to be designed and engineered. The engineers at Foundation Technologies provided us with an engineered design to secure the required load capacity within the soil configuration.
The structure was directly perpendicular to the salty waters of the Caloosahatchee River, located in a finger canal. The engineered helical system would be installed two (2) foot beneath the proposed 6-foot deep swimming pool to a finished designed depth of eight foot. The new vinyl wall could then be attached to our secure helical piles.
PROJECT OUTCOME
Coastal Foundation Solutions, a contractor that also specializes in marine construction work, always performs our work with precision. With our helical pile experience and technology, there is no pounding and little chance of debris shooting away and hitting boats or adjoining homes. The Town and River seawall project was completed in just a few short days (including material and equipment mobilization). It was another great experience for us, and a successful installation, specifically due to the subsurface soil conditions.
Products Installed:
- Twenty-two (22) Seawall Savers SS125 (1 1/4-inch square bar) helical tiebacks with an 8”- 10”- 12” triple-helix lead section with an additional 14” helical extension was installed.
- A Caterpillar 305 CR 12,000-pound excavator with a specialized hydraulic drive head (10K Pro-Dig) was used to rotate anchors into the ground.
- Helical extensions advanced the tieback anchors to distances on the distance of 21 to 28 feet to realize final installation torques.
- The ultimate capacities and design working tension load of 15 kips.
Helical Anchors
- Twenty-two (22) “Chance SS125” square shaft helical piles with an 8”-10” 12” triple-helix lead section were installed into substrate.
- Twenty-two (22) “Chance SS125” square shaft helical with a 14” lead extension section were installed in addition to the prescribed lead section.
- Fifty-five (55) “CHANCE” (SS125) square helical extensions were installed to corresponding capacities to secure compression load design load requirements.
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