A recognized challenge for geotechnical engineers designing deep foundations is utilizing information on subsurface soils from a finite number of subsurface explorations (e.g., test borings with Standard Penetration Test sampling). If the geotechnical engineering consultant that was hired to coordinate and report on the explorations performs their work within the standard of care, the number of explorations performed at the site is appropriate and useful for characterization of a site’s soil profile. From a well-coordinated subsurface exploration program, a geotechnical engineer is able to develop a representative understanding of the composition and strength of subsurface soils (including rock and obstructions where present) at a site. It’s no mystery that SPT boring logs per ASTM D-1586 are routinely used in the design of deep foundations, especially considering the many empirical correlations between SPT blow count and engineering properties of soils that have been established since the test method was standardized in the mid-1950s.
A bit more obtuse than my last article, but definitely something to think about are the broader impacts that helical piles can influence when expanding the focus from product-specific sustainable features to a broader capital-S Sustainable community perspective…
For buildings and structures, material selection, energy conservation methods and good water efficiency are important parts to consider when thinking of sustainability. However, thoughts about what could be considered a sustainable foundation are often overlooked (or don’t go much “deeper” than costs or what LEED points it can qualify for). Let's explore how CHANCE helical piles effect the environment, economy, and society to create a more holistic view of what it means to be sustainable.
On land, piling and anchoring solution are abundant and helical anchors have always been known to be cost-effective, versatile, and easy to install. Offshore, however; helical anchors stand alone as the superior choice for mooring applications. First used in the marine environment to secure oil pipelines to the ocean floor, helical anchor technology has been proven to be a successful and environmentally sensitive alternative to traditional mushroom, deadweight, and pile anchors for boat owners, harbormasters, and marine construction and civil engineering firms.
Dry Tortugas National Park is home to historic Fort Jefferson which was constructed for the protection of valuable shipping lanes in the Gulf of Mexico and along the eastern seaboard. The small remote island, only accessible by boat or seaplane, is located 70 miles west of Key West in the Gulf of Mexico and is surrounded by waters, beautiful coral reefs, and protected marine life.
All Engineers can relate to an experience we’ve had where what we designed was not how it turned out in “the real world”. Rarely does a project end up being exactly as what we put down on paper. Soil testing for foundation supports is no exception and unfortunately these differences almost never end on the positive side of a cost estimate.
Hurricane Sally left a path of destruction across Alabama including this residence that was constructed on a bluff overlooking Perdido Bay. The seawall protecting the home failed during the storm and washed portions of the yard into the bay. The rear of the house saw extensive foundation damage that left the foundation completely exposed and partially undermined. This damage left the house susceptible to further foundation settlement and major structural damage. Access could only be gained by water and vibration from equipment or installation of piling could possibly further erode the foundation. Based on these site conditions it was determined that small equipment and helical piles were the best choice for foundation remediation.
Installation of CHANCE RS2875.276 helical piles with the C1500121 CHANCE Standard Underpinning Brackets were completed by local installer Mason Grady Foundations. A mini excavator was brought to the site on a barge from Perdido Bay. In total 15 helical piles were installed to a depth of 25 feet into the underlying bearing stratum. Due to the excessive pile reveal required, column buckling was a concern at the pile head connection. To provide additional lateral support a 6” diameter PVC sleeve reinforced internally with a rebar cage and filled with structural grout was placed around the top section of each helical pipe shaft.
Despite the access and site conditions Mason Grady Foundations was able to successfully stabilize this home in five days. The expedient install of the CHANCE underpinning systems was vital in keeping the home from having further structural damage. A new tieback seawall is planned to be constructed along Perdido Bay. This seawall will use CHANCE helical tiebacks to restrain the wall and offer enhanced protection from future natural disasters.
Modern infrastructural design and architecture are evolving due to rapid improvements in modern technology and material science. This has raised the bar, calling for construction and engineering companies to rise to the occasion with improvements in foundation systems.
Obstructions can be difficult, because you often do not know they are there until you begin to install a deep foundation. Helical piles cannot install through obstructions; however, here we highlight the different options you have for dealing with obstructions while installing helical piles. One of the benefits of helical piles is that you do not have to abandon the pile. In most cases, it can be removed and reinstalled (unlike other deep foundation options).
Helical piles are an excellent foundation solution for the oil and gas industry, both in congested and remote areas. They are easy to install and can be uninstalled (if necessary) and reused at another location. They are displacement piles, so they produce no spoils, no time is lost waiting for concrete to cure before loading, and they are installed with minimal environmental impact. For oil and gas applications, helical piles can be the most suitable foundation solution in the segment.