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CASE STUDYSWIMMING POOL STABILIZATION

HELICAL FOUNDATION SUPPORT FOR SWIMMING POOLSPROJECT INFORMATION

Walk onto Southwest Florida’s hidden gem, St. James City, and you may never return home again. The 7-mile drive south from the 4-way stop at the Pine Island Center provides a trip back in time to Florida’s old country. The unspoiled bay waters, breathtaking sunsets, and delicious seafood at waterfront eateries have the trappings of an exotic, tropical island without even having to exit the country.

HELICAL PILES FOR SWIMMING POOL SUPPORT

Most waterfront neighborhoods have a history of home settling, which often proves to be a good indicator that you have poor soil conditions that require additional foundation support for the pool structure. If you live in an area within close proximity to water, there is a high probability non-engineered fills were used to build your existing house pad. These fills in and of themselves are not unhealthy, but today’s engineers are very dubious of building structures on questionable fills and may specify helical pilings for additional foundation support.

PROJECT CHALLENGES

Swimming Pools are often installed adjacent to waterfront shorelines, which have high levels of unstable or organic soils. This creates settling over an extended period of time can cause severe cracking and associated problems. These symptoms usually entail both extensive and expensive repairs. The general contractor for this project ordered a geotechnical analysis to identify the soils conditions, to provide better insight for proper foundation stabilization.

The soil report revealed serious peat material beneath the existing grade consequently requiring a helical piling foundation. The pool engineer provided the design and load bearing capacity. The number of anchors required, their location and capacity, are also determined by an engineer during the design stage and are included on our structural plans.

SWIMMING POOL HELICAL INSTALLATIONTHE SOLUTION

ENGINEERED HELICAL PILES

Helical piles were determined to be the effective and practical solution for this project. The engineered design for the pool and deck included twenty-two (22) “Chance” combo piles which included a 1 ½ square shaft piling attached to 2.875-inch OD by 0.276-inch wall helical piling. Square shaft helical piles with 8”-10”-12” triple-helix lead sections were utilized. The piles would support design working loads ranging from 12 to 30 kips. With the presence of the fill and weak native soils near the original ground surface, a minimum helical pile depth of 21 to 35 feet, as measured from pool deck sub-grade elevation, was required.

EQUIPMENT

A Caterpillar #305 CR track excavator was fitted with a custom mounting bracket to support the drive head with a rated output torque of 10,000 ft-lb. Peat was discovered during the preliminary helical pile installation, requiring additional pile advancement and affecting torque accuracy. Additional extensions were required reach the specified load capacity and structurally-tolerable parameters. The piles were advanced to depths ranging from 21 to 35 feet to achieve torque-correlated ultimate capacities of at least twice the design working loads. The tops of the piles were cut to design elevation and tailored with new galvanized construction brackets to be cast into concrete grade beam. The 22 helical piles were installed over the course of just two days.

HELICAL FOUNDATION PILING

The helical piles were installed by Coastal Foundation Solutions (CFS), a Certified Installer of Seawall Savers and Chance Helical Foundations Systems.

  • Twenty-two (22) CHANCE 1 ½” square shaft helical piles with an 8”-10” 12” triple-helix lead section were installed with a 10K Eskridge drive head.
  • The Caterpillar excavator progressed the extensions to lengths on the order of 21-35 feet to achieve final installation torques.
  • The ultimate capacities of at least twice the design working tension load of 20 kips
  • Twenty-two (22) 1 ½” SS150 Square Shaft/RS2875 Round Shaft transition couplers.
  • Sixty-eight (68) “CHANCE” (RS2875.203) round helical extensions were installed to corresponding capacities to secure tension load of 20 kips.
  • The helical foundation pilings were affixed with a galvanized 7’ by 7” termination cap.
  • The helical piling installation was completed in three days due to access constraints.

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