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Spring 2004 |
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Cover Story
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The story of Iowa State's involvement in the fastest growing foundation company in the world began with a student, and idea, and a relationship. The first Baptist church in Columbia, South Carolina, had a problem. Their building project was a quarter-million dollars over budget. They were determined to proceed, and just as determined not to spend more than they could afford. A significant determinant of a building's cost is its type of foundation, and so they contacted geo-engineer Nathaniel Fox, who had a new, cost-saving idea. "It  was surprising that I got the project," Fox remembers. "I'd done only tiny projects and had no track record. If they hadn't been so desperate to save money, they wouldn't have risked it."Nathaniel Fox did, in fact, have a track record. He began receiving patents for his inventions in the mid-1960s as an Iowa State Ph.D. student in civil engineering. Twenty years later, he was ready for a challenge. Today, the solution to that challenge, called Geopier™ foundations, has become a $50-million-dollar-a-year international business. Instead of driving deep piles into the earth-an expensive operation because of its drilling technology-Fox drilled short columns, filled them with crushed rock, and tamped them down. Engineers expect buildings to settle into their foundations about one inch  . "I'm almost embarrassed to report how much the building settled," remembers Fox. "Geotechnical engineers might think I'm exaggerating—or worse—when I say it was 1/8 of an inch. That amount of settlement was unheard of. The system was very effective."His former major professor, Richard L. Handy, ISU Distinguished Professor Emeritus of Civil Engineering, remembers receiving a call from Fox. "The fact that he couldn't measure any substantial settlement had him worried. I said to him, 'This is a bad thing?'" Fox wasn't worried as much as he was perplexed. Why did his columns work so well? "It's an intuitive, simple idea that has taken us years to understand," he says. "Dr. Handy has been my main guy to explain it. He's my mentor and my hero, and he's an absolute genius in the field of geotechnical engineering worldwide." Traditional methods of supporting buildings—dispersing their weight throughout the soil so that they don't settle—are thousands of years old, Fox says. To support lighter structures, such as houses, foundations are created by digging a large, shallow hole and building a concrete pad. For heavier buildings, deep foundations are created  by pounding long, slender steel rods anywhere from 30 to 100 feet into the ground."Up until now, a consulting engineer has one primary question to answer on every design project that he does," explains Fox. "That question is: Can this structure be supported on shallow foundations, or does it need to go deep? Is it an inch, or is it a mile? Now he has another option: it can be intermediate." And if an intermediate foundation is required, the building engineer is increasingly likely to use Fox's Geopier foundations. Holes for the piers, with diameters ranging from 8 to 36 inches and depths of 20 to 30 feet, are drilled quickly. A stable "bulb" is formed at the bottom of the hole by filling the cavity with crushed aggregate such as gravel, limestone, steel byproducts, or concrete from ripped-up pavement, then ramming the filling both vertically and laterally with a patented tamper. Layers of rock are added and pounded at intervals of about 12 inches, forming a column of support that is both strong and inexpensive. Its strength, Handy has discovered, comes from the lateral pressure of the rocks. The job of researching Geopier foundations and their applications, begun by Handy, is being continued today at Iowa State by David White, assistant professor of civil and  construction engineering. "It's a pretty complicated system," explains White. "It turns out that the behavior of soil is affected by lateral stress. When you ram rock into a hole, it causes the hole to expand, and when it expands, it builds up a lot of lateral stress. And lateral stress makes the piers stiffer and stronger vertically." Another factor important to the success of the Geopier foundations, White explains, is the angle of the beveled rammer, patented by Fox in the mid-90s.To date, more than 400 load tests have been conducted on Geopiers in Europe and Asia. Investigators at Iowa State, the University of Utah, the University of Massachusetts-Amherst, and Virginia Tech are conducting research on transportation applications of Geopier foundations, including bridges, culverts, and railroad embankments. Nine of 15 recent transportation projects were constructed in Iowa. Originally, the primary purpose of Geopier foundations was to strengthen weak soils. However, 15 years after the original concept was developed, Fox finds that 60 percent of his projects have been constructed on average and good soils. His marketing niche has become the economics and performance of an intermediate foundation system, successful both in the United States and in developing countries. "Its success is its simplicity," says David White. And why hadn't anybody thought of it before? "It's sort of untraditional. A lot of engineers get comfortable with a practice and stick with it. Nat Fox has done a really good job of educating and marketing. The system is having an international impact." |
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