It’s an unlikely spot for a fancy new bridge. But the farmers who’ve been driving a two-mile detour for the past 20 years are quite pleased. Smack in the middle of the farm fields and prairie that blanket windy Rock County just east of Luverne in the far southwestern corner of Minnesota, you can find the state’s first Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS).
The Federal Highway Administration (FHWA) teamed up with MnDOT and Rock County to build the bridge between snowstorms this past spring as a way to introduce the technology to wary public works officials in the state and to conduct further testing. A daylong showcase event in June, which included a tour of the project site, drew around 40 participants from five states, mostly engineers. The event was the third demo nationally of GRS-IBS as part of the FHWA’s Every Day Counts initiative.
The method uses alternating layers of granular fill and sheets of geotextile reinforcement.
There are now more than 100 of these bridge systems around the country. The GRS-IBS technology uses alternating layers of compacted granular fill material and fabric sheets of geotextile reinforcement to provide support for the bridge instead of conventional supports. The simple construction method can lower costs, slash construction time, improve durability, and increase worker safety.
“We’ve always had this location on our list of projects to do, but we never had the funding to do it,” said Rock County Engineer Mark Sehr. “With the assistance of Federal Highway and the Minnesota DOT, we were able to fund this project and, therefore, we’ll get one of our roadways open that’s been closed for a number of years.”
And if everything works out as planned, there’ll be no bump between the bridge and approaching roadway caused by uneven settlement. Eliminating that characteristic of conventional bridge systems is a key feature of the new technology.