9:58 a.m., Jan. 30, 2009----With funding from the Delaware Department of Transportation (DelDOT) and significant in-kind contributions from a number of companies, Christopher Meehan, assistant professor in the Department of Civil and Environmental Engineering at the University of Delaware, is investigating a new construction technology known as intelligent compaction (IC).
“Any time soil is placed during construction - whether it's for a road, an embankment, or an earth dam - it needs to be compacted,” Meehan says. “The compaction process determines the ultimate engineering properties of the soil, including the shear strength, compressibility, and permeability, and these properties are critical to the design of earthworks structures.”
The traditional approach to compaction has been to drive a roller over the soil after each layer is deposited. Testing is then done by a field fill control engineer, who “spot tests” areas throughout the construction site.
“The problem with this approach,” Meehan says, “is that there is no control of the compaction process itself, and selection of the areas to be tested is subjective. Also, the volume of soil that's actually tested is only a very small fraction of the amount that's compacted, so we're making assumptions based on limited information.”
Intelligent soil compaction, an emerging technology, has the potential to improve infrastructure performance and safety, decrease costs, and reduce construction time. The new technology uses advanced monitoring and control tools to manage compaction as well as satellite-guided GPS systems to guide the use of the equipment and provide a comprehensive record of the compaction-related earthwork.
According to Meehan, major equipment manufacturers such as Caterpillar have already begun to incorporate new intelligent compaction tools into their products, but research data is needed to transition the use of the technology to actual practice. “We have to show very robustly that it works before it can be incorporated into state construction specifications,” Meehan says.
Conducting such research at an actual construction site can be difficult, given typical project contract issues, so the five-day field study conducted by Meehan and his students last summer occurred at a site near Odessa, Del., donated by Greggo and Ferrara, Inc., a construction company located in Wilmington. The company also donated the fill materials as well as the use of a Caterpillar front-end loader and a water truck. Caterpillar donated additional equipment and operators, software, and on-site technical expertise.
“We basically built the sub-base for a road just the way that DelDOT would do it,” Meehan says. During this process, the site was used to collect data that will enable comparison of several approaches: the current method, several state-of-the-art technologies for in-situ testing, and the new IC equipment.
The project is currently in the data analysis phase, which will be completed by summer 2009. “We're looking forward to providing hard data that will support implementation of this new technology,” Meehan says. “But aside from the research findings that we expect to emerge from the project, I am amazed at the overwhelming support we received from industry to allow us to do this work. The project also provided great field experience for our students.”
In addition to Greggo and Ferrara, DelDOT, and Caterpillar, the project was enabled by donations of materials, equipment, and expertise from Giles and Ransome CAT, Kessler Soils Engineering, Humboldt Manufacturing Company, the Electrical Density Gauge Corporation, and the Maryland Department of Transportation.
“It was truly remarkable,” Meehan says. “At any given time, we had about a dozen people at the site, and the only one actually being paid from the DelDOT grant was a graduate student whose master's thesis will document the research findings. All of the people out there, including the five other grad students, were donating their time so that we could get this work done.”
“This intelligent compaction project has a lot of potential benefit to DelDOT and the contracting community,” says Jim Pappas, chief materials and research engineer at DelDOT. “Potential benefits include quicker information gathering for both DelDOT and the contractor, real-time information for the equipment operator, and efficiency increases for the contractor.”
“At this point, the IC work is still in the experimental phase,” he continues, “but many industry people are seeing the potential benefit, so the timing of this work by Chris and his team is very good.”
Article by Diane Kukich