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When in Doubt, Grout!
Larger diameter helical pipe piles and drilled-in displacement piles have become increasingly popular of late as deep foundation solutions. This popularity is justified for a number of good reasons, but these newer options are sometimes used, perhaps overused, at the expense of a slightly older technology that still has a well-deserved place in the deep foundation firmament. It was only a short while ago that grouted helical piles were the new kid on the block. Danbro Distributors played a prominent role in the evolution, refinement, and acceptance of grouted helicals and are firm believers that there is still an important niche for this under-used, under-appreciated technology. 2019 is the fifteenth anniversary of the original largest grouted helical project, Tasker Homes. A retrospective on Tasker reminds us why sometimes, to get ahead, you need to go back and revisit a solid technology that still works.
The long and winding road (apologies to the Beatles) for grouted helical piers begins in January of 1998 with Dr. Robert Vickars, patent holder and inventor from the Canadian Province of British Columbia (U.S. patent (5,707,180)). It leads to Centralia, Missouri, and the A. B. Chance Company, the exclusive licensed manufacturer of the then-new technology. It continues to Installer networks throughout Canada and the United States with a particularly significant landing in Philadelphia, Pennsylvania, with Danbro Distributors.
In the late 1990s, the Philadelphia Housing Authority (PHA) was taking a hard look at public housing. A lot of older high-rise construction, derided as “the Projects,” was crumbling and needed to be refurbished or replaced. Relying on the consensus of urban planners, social scientists, and the PHA, who advocated for fostering community and pride of ownership by creating neighborhoods, the PHA embarked on a series of projects that would replace older high-rise housing with neighborhood townhouses. The first two neighborhoods, compatible with the surrounding residential landscape, featuring less density and more open space, were Raymond Rosen Phase I in 1997, followed by Raymond Rosen Phase II in February of 1999. New beginnings and a fresh approach lend itself to new ideas/technology and helical piers were used for foundations for both townhouse neighborhoods. Keeping with the theme, helicals were more neighbor friendly with no spoils, no vibration, smaller equipment, and less noise.
Tasker Homes is located on the Schuylkill Expressway, one of Philadelphia’s main arteries, and the new development (2003) would be on display to virtually the entire city. This development would be a highly visible showcase for this new approach. Everything had to go just right. The old buildings were demolished creating an upper layer of debris underlain by urban fill. Conventional strip and spread footing would require over-excavation, backfill, and costly soil removal. Timber piles were originally specified, but vibration concerns and multiple mobilizations led the PHA and their construction/engineering advisors to look elsewhere. Helicals worked well at Raymond Rosen, but the soil conditions at Tasker were much different, raising concerns about segmented, steel piles. The load test summary on page 6 of the attached DFI whitepaper on Taker Homes demonstrates why all the concerns about this relatively new technology went away… poof! The deeper the pile, the more capacity was derived from the skin friction on the shaft. The grout alleviated all design concerns regarding lateral, buckling, and corrosion.
Tasker Homes became a showcase for thoughtful (click here to read project whitepaper), well planned public urban development, literally from the ground up. Grouted Helical Piles played a significant role in the innovative thinking and execution by the PHA and their construction and engineering partners. This very public project with 3,645 Grouted Helical Piles helped put this relatively new technology on the map and paved the way for the extensive use of Grouted Helical Piles in Environmental Remediation and Super Storm Sandy work. The Danbro Installer network has installed more Grouted Helical Piles (cased and uncased), in various soil environments and diverse applications, than any other installer group in the country.
Deep foundation innovations continue, but the professional community would be wise to consider all their options and remember an old, reliable, economically viable alternate to newer more expensive piles. Our cautionary mantra at Danbro continues to be, When in Doubt, Grout!
by Pat Haffert
Danbro Vice President
3700 South 26th Street
Philadelphia, PA 19145
Phone: (215) 271-7700