HELICAL TIEBACK INSTALLATIONPROJECT INFORMATION
Fort Myers Beach lies on beautiful seven-mile coastline that has captivated the imaginations of visitors from near and far. Estero Island has quaint cottages, Old Florida charm, fresh seafood from the Gulf of Mexico and the annual Shrimp Festival.
Sunshine and water, water everywhere! Situated on a point at the south end of the island, is the delightfully landscaped Harbour Pointe Condominiums providing gorgeous views of the Estero Bay. No need to rent a boat, the condominium shoreline boasts it’s on reef in the backyard. Loads of family fun for all the fish you are going to catch. Unsurpassed private beaches after your walk down Bay Beach Lane – seven miles of turquoise Gulf waters and white sand await you.
HELICAL TIEBACKS FOR A NEW VINYL SEAWALL
Florida Marine Construction was selected most responsible bidder on a project entailing installing 1,000 foot of vinyl sheet piling. The project was immediately adjacent to the entrance drives to multiple condominium residences, which also provide emergency access to the units. Consequently, the existing twenty-eight foot paver driveway could not be disrupted in any way.
Turrell Hall and Associates engineering and design team confirmed the scope of work and designed a helical tie back system for the project. The Project Manager in charge of the renovation met with the Board of Directors and secured approval for installation of helical tie-back anchors. The driven screw piles would have to be installed in order for the anchors to avoid clashing with the existing driveway structure and subsurface utilities.
PROJECT CHALLENGES
Coastal Foundation Solutions were approached to assist in a solution for marine foundations at the condominium project. The marine contractor had a few challenges of its own to overcome and realized the benefit of hiring CHS as a subcontractor.
The structural engineer in charge of the design of the seawall project provided the pile loadings and the layout of the screw pile anchors to Coastal Foundation Solutions. This information came along with the soil report of the location, which confirmed the presence of clays in the layers beneath the water.
Site access and bulkhead positioning was limited, so screw pile tie-back anchors were identified as the best solution by the Client and the Engineer. The screw piles were to be installed behind a new vinyl seawall and next to a major access drive; therefore they required a vibration free and non-destructive installation method to prevent driveway damage.
HELICAL TIEBACK ANCHORSTHE SOLUTION
We used our Cat 311D ( 30,000# excavator) with a 10K anchor pile driver due to distance requirements and reach, ensuring a smooth installation. There was no damage to the pavers or underground utilities. The screw piles transferred the load from the soils to top of the new seawall to prevent it failing due to the additional loads of the access road structure.
Our screw piling were specified by the Foundation Technologies engineer team and they were ideal for supporting the loads (up to 8 tons per pile). The 10” x 12” helix pile system was rotated into the shoreline bank at distances of 14 foot to 42 foot. Our screw piles are unique in not requiring any concrete trades, thus removing the time delay in the construction for curing of concrete.
PROJECT OUTCOME
At Coastal Helical Solutions, we positively focus on the skilled applications that benefit our helical piling systems. This includes marine structures, new home construction, swimming pool construction and environmental and civil engineering productions. Helical piling and screw piles have been employed successfully for years in multiple piling applications.
Why were helical tieback anchors chosen for this Harbor Point Condominium application? Applying screw pile tie backs provided the following benefits:
- Less energy required to provide tension load capacity
- Smaller disruption of the soil due to slimmer core tube
- Capability to thread helical anchor around utility pipes
- Lighter equipment used which equals less noise
- Absolutely no disruption or inconvenience to condo owners
PRODUCTS
One hundred fourteen (114) “Chance Screw Anchor Pilings” SS5 Square Shaft Helical Pile (1-1/4” x 1-1/4”) new foundation pile with a 10”- 12”- double-helix lead section was installed into a compacted dense soil.. The screw anchors were rotated to tension capacity with a specialized hydraulic drive head (12K Digga). Helical extensions progressed the tieback anchors to distances on the order of 14 to 42 feet to realize final installation torques. The ultimate capacities and design working tension load of 16 kips.
One Hundred seventy-two (172) seven (7) foot SS5 Square Shaft Helical Pile (1-1/4” x 1-1/4”) extensions were utilized to reach required load capability due to sub-surface soil variations and debris.
In addition, we installed one hundred fourteen (114) three (3) foot extensions to close the gap between the vinyl wall panels and screw piling termination ends.
The helical tie back anchor was linked to a hot dipped galvanized steel channel, placed within the new seawall cap to provide lateral structural support. The tiebacks and anchors were load tested with a 30-ton center pull ram to secure required engineered load capacity of 16 KIPS.
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