Researchers from the University of Texas at Arlington (UTA) have developed a technology to slow the settling of roadways and bridges.

Workers installing geofoam blocks under a highway. Image source: UATThe approach uses geofoam blocks—which measure about 6.5 feet by 2.5 feet by 2.5 feet—to support the earth underneath roads and bridges. Such foundations often are made up of soft and compressible soils because of their proximity to water.

Anand Puppala, associate dean for research in the College of Engineering, says “a good number” of the 52,000 bridges in Texas have “bump” problems on entry because of settling soil under the pavement slabs.

The research is supported by an implementation grant from the Texas Department of Transportation, and allows Puppala and his co-researcher, Assistant Professor Xinbao Yu, to test the geofoam blocks.

“If you place something heavy, like a road or a bridge, on soft soil, it will stress the underlying soil which gets compressed with time,” says Puppala. Geofoam blocks cut down on sediment, can be stacked and do not place stress on the soil, so structures are safer and more stable. He says they also are designed in such a way that they do not degrade, making them environmentally safe.

Geofoam blocks have been installed near a bridge in Johnson County, Texas, to slow the rate of settling at the bridge entrance; the area has settled 17 inches since 1995, or about one inch a year.

The UTA research team replaced an embankment near the bridge with geofoam blocks in 2012. In the three years since the installation, the team has measured less than one inch of settlement.

‘”Several methods were used previously to try to stop the settling, but none worked,” says Puppala. The research team is discussing using the material at other bridge sites.