******11-19-2007. Helical Pier World has just been notified by Foundation Drilling Magazine that the article Truth in Advertising by Tom Witherspoon is now available.*******
Helical Pier World Under Fire
In a recent article titled “Truth in Advertising,” that appeared in Foundation Drilling magazine in July, 2007, HPW was discredited as simply an advertising arm of the helical pier industry based on a series of articles published in HPW’s Moments newsletter and website. We were accused of presenting information that was not only “apples vs. oranges,” but was also void of “hard research,” and based purely “on promotional materials.” We have extracted the relevant quotes for the purposes of this article.
The series that is “Under Fire” appeared on Helical Pier World and was titled “A Tale of Two Projects,” and its two follow-ups; “A Tale of Two Projects Part 2,” and “A Tale of Two Projects Part 3.” Please don’t hesitate to re-read this series and re-acquaint yourselves.
The author of the “Truth in Advertising” article, Tom Witherspoon, PhD, P.E. misses the crux of the series entirely, and instead focuses on the performance of individual foundations and their performance based on a study that he performed. First, you should educate yourselves on his study and HPW encourages you to read it. It is titled “Side by Side Axial Load Testing of Residential Underpinning.” First let HPW spell out what the HPW series was all about (the crux) and what it wasn’t, then we’ll address the specific statements that Dr. Witherspoon makes regarding the inferiority of helical piers.
The Crux. The “Tale of Two Projects” is so named because it compares projects, not individual foundations. The series isn’t about whether a 12” drilled shaft is better than a helical pier of similar size. That is not germane to the series. It is about what foundation system is more efficient. Each foundation system on each of these projects was engineered to support the given loads for that project, so talking about load capacity of individual foundations is completely irrelevant. This series was meant to highlight the speed and efficiency of using helical piers over drilled shafts on a given project.
Although Dr. Witherspoon misses the crux, he does bring up some discussion points. Very quickly, HPW shall address each of his main points only as they pertain to “The Tale of Two Projects”. This is by no means a complete and consolidated answer on behalf of the entire helical pier industry, so please do not take it as such.
- The HPW series was about two very similar projects with different foundation system choices. Dr. Witherspoon says that “This comparison is apples and oranges.” The projects were of extremely similar scope, within eye site of each other, and started on the same day. Aside from controlling all variables in a laboratory setting, this is as close as one can get for an in situ comparison. Not only was this apples to apples, but it was macintosh to macintosh.
- “The helicals will have much less axial capacity than a drilled shaft of comparable diameter and depth.” There are two potential answers to this statement and one major issue. The answers depend on what Dr. Witherspoon considers the diameter of the helical pier to be. Is it the diameter of the shaft or of the helical plate? To make the statement that he did, he must assume the helix diameter as the diameter of the helical pier. The issue with this statement is “who cares?” When designing a foundation for a project there is no limit on foundation diameter. The engineer designs the foundations to accommodate the loads for the project. Different foundation types will have different sizes and quantities, but each type is a suitable solution.
- “Then there is the very critical problem of settlement when installing helical piers.” “As proven….helical piers will have significant initial deflection before reaching ultimate load.” There are a myriad of factors that could cause any foundation type to settle initially. One reason that helical piers can experience some initial settlement is due to compression of the connections between the sections. This settlement typically isn’t anywhere near the “1” to 3” deflection” that Dr. Witherspoon claims to have witnessed. That said, the helical piers used in the HPW series did not have any connections. They were also designed to be end bearing. The piers were also load tested on site and were within deflection limits.
- “Usage of a trailing helix will not increase the axial capacity…” “ ...axial capacity of single and double helix showed very little difference.” I’m not going to spend too much time defending multiple helixes here since the helical piers in this series were single helix, not to mention that there are copious volumes of research that refute this ridiculous claim.
HPW finds it amusing that it is being accused of bias, simply by promoting helical piers. A helical pier website promoting helical piers. Go figure. And the article accusing HPW of such bias and promoting drilled shafts, all the while appears in a Foundation Drilling magazine. And we are supposed to assume objectivity there?
Helical Pier World
