2/12/2010
“Being able to gather on-site data offers a rare opportunity for engineers. The experience helps us to visualize the scale and better understand the circumstances where failures occur than we could get from photographs.” That’s why Scott Olson went to Haiti.
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“Being able to gather on-site data offers a rare opportunity for engineers. The experience helps us to visualize the scale and better understand the circumstances where failures occur than we could get from photographs.” That’s why Scott Olson went to Haiti.
“Without going into the field and documenting the actual sites, we don’t have good case studies,” explained Olson, a professional engineer and assistant professor in the Department of Civil and Environmental Engineering at Illinois. He was one of nine engineers and scientists on a Geo-engineering Extreme Events Reconnaissance (GEER) team that went to Haiti to study ground failures such as liquefaction and landslides during the magnitude 7.0 earthquake on Jan. 12. The GEER association is funded through the National Science Foundation and the National Earthquake Hazard Reduction Program (NEHRP).
“Specifically, we were looking at damage related to fault displacement, liquefaction, landslides, and other ground failures," Olson said. "These failures can involve port structures (as was the case in Port au Prince), buildings and their foundations, levees, embankments and dams, slopes, storage tanks, tunnels, and other geostructures.
“There are a limited number of well-documented cases of liquefaction, which is a process of a sand deposit transforming from a strong, granular mass to a thick, viscous liquid--think 'quicksand'--as a result of seismic shaking. We took hand-operated measuring equipment with us so we could do field testing.”
Olson, who is also an Illinois' alumnus (BS 1993, MS 1995, PhD 2001, Civil Engineering), primarily studied two wharfs at Port au Prince to determine the soil quality.
“The wharf at the port was completely destroyed,” he said. “About 50 feet of the north wharf pulled away, and the huge loading cranes just followed along into the bay.
“After testing, it was apparent that the ground was much too loose to build on,” he explained. “It goes back to the fact that there is not much heavy construction equipment available, so they are unable to compact the ground properly to prevent earthquake damage.”
Olson explained that soft soils tend to magnify ground motions. In addition to the ground failures along the coast, about 40% of the buildings in Port au Prince had collapsed—that amount rose to about 75% for buildings in the other towns. Massive landslides blocked the roads and cut off many rural parts of the country.
“One thing we did learn: a lot of the damage was due to horrible construction practices.” Olson noted that wood-frame structures and those with metal roofs performed better than other all-concrete buildings with heavy concrete roofs. The collapsed concrete buildings often were constructed with undersized or insufficient amounts of rebar (or steel reinforcing bars), and smooth river gravel was often used rather than crushed aggregate in the concrete. He also noted that much of the mortar used in masonry construction probably had low-quality lime and was mixed with too much water—making it cheaper, but much weaker than cement mixes used in the U.S.
The GEER survey team concentrated on ground and soil conditions. Because of the variations within different types of soils and conditions, it is very difficult to create computer models that can predict the effect of earthquakes. But Olson thinks the researchers will be able to associate the soil densities with the damage patterns. Further work by structural engineers will gather similar information and make recommendations about improving buildings.
“I joined the GEER association a couple years ago,” Olson recalled. “When an event like this happens, they take volunteers from the list, and supplement it with a few other experts to build an on-site team.”
“Our big-picture goal is to increase our understanding of soil under buildings, dams, and ports so we can better predict when and where liquefaction might occur in the U.S. and around the world. Hopefully, it will allow us to reduce ground-related failures in developing countries.”
Led by Dr. Ellen Rathje, a civil engineering professor at The University of Texas at Austin, the GEER team also included Jeff Bachhuber of Fugro/William Lettis and Associates, Dr. Brady Cox of the University of Arkansas, Jim French of AMEC/Geomatrix, Dr. Russell Green of Virginia Technical Institute, Dr. Glenn Rix of the Georgia Institute of Technology, Oscar Suncar of The University of Texas at Austin, and Donald Wells of AMEC/Geomatrix. The GEER association is funded through the National Science Foundation and the National Earthquake Hazard Reduction Program (NEHRP)
The GEER team members lived in tents on the grounds of a partially completed, partially damaged hotel, with water and power available for about two hours a day.
So, what did he take away from the experience?
“Well, it reminds us why we are engineers,” Olson stated. “We observed liquefaction at the ports and ground failures that occurred at the port,” he added. “Our final report will include proposals for ways to improve the ground, for example, by using more locally available wooden piles for support. The recommendations need to include things that can be accomplished in a place like Haiti.”
Olson will present a seminar, "Snapshots from Haiti: An Engineering Perspective," on Tuesday, Feb. 16, 11 a.m.- 12 noon, B02 Coordinated Science Laboratory (auditorium). In this seminar, Olson will present his first-hand observations on damage to buildings, roads, ports, coastlines and hillsides. In addition, he will describe aspects of how these engineering failures complicated and often delayed humanitarian relief efforts.
On February 16, WILL-AM aired an interview with Scott Olson about his experiences in Haiti. Listen to that interview at http://will.illinois.edu/news/story/haiti021610.
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Contact: Scott Olson, Department of Civil and Environmental Engineering, 217/265-7584.
If you have any questions about the College of Engineering, or other story ideas, contact Rick Kubetz, Engineering Communications Office, 217/244-7716, writer/editor.