The Indiana Department of Transportation pioneered the use of the styrofoam-looking material geofoam in 1995 to international fanfare and occasionally uses it today, including at the high-profile I-69 Finish Line project.
Geofoam is a lightweight, geosynthetic fill material used as an alternative to various fill materials. It has been used only 15 times at INDOT, with the latest being 2021 at I-69 in Martinsville to stabilize the soil around the new State Road 252 interchange and as part of the fill for the new S.R. 252 bridge.
Geotechnical Consultant Design Group Manager Mir Zaheer noted that the weight of geofoam is only 1% of the weight of soils, or nearly 100 times lighter. It’s also 30 times lighter than other lightweight-fill alternatives.
Geofoam can be placed in all seasons and provides many benefits,” said Zaheer. “It enables rapid construction by eliminating construction schedule restraints caused by preloading, surcharging, and staged construction. Reducing total settlement and minimizing differential settlements means faster construction of embankments.”
Geofoam is a soil alternative, so its embankments can be covered to look like normal sloped embankments or finished to look like a wall. That’s what happened on the I-69 Finish Line project.
INDOT has used low-density, high-strength, and long-lasting geofoam in areas where soils may be prone to shifts. Geofoam stabilizes heavy structures, like overpasses, in these areas. The use of lightweight, durable geofoam results in a much lower impact on the surface soils compared with other methods.
INDOT’s first use of geofoam came in 1995 and was praised internationally because it was cutting-edge technology at the time. A 1,100-foot section of State Road 109, 2 miles south of Wolf Lake in Noble County, failed. We closed the road because of a large dip in the pavement caused by the presence of peat bogs beneath the roadway. A layer of peat ranging from 25 to 38 feet shifted, sank, and created roadway settlement.
“To date, all projects where geofoam has been used have performed very well and in accordance with the design performance criteria set,” said Zaheer. “We will continue to recommend geofoam for use on future projects where there would be a need for this product.”