The Stearns County Department of Transportation relied on the Spectra Roadway Improvement System to treat a 2.5-mile-long section of weak subgrade. County State Aid Highway (CSAH) 115 had been repaved and patched repeatedly over a 20-year period. Each time the repairs quickly degraded, causing the roadway to fail. Adding to the challenge was the fact that sections of the route traverse swamp-like soils with low shear strength (CBR=1.5%). County Engineer Jodi Teich noted, "The site contained the worst soil conditions in Stearns County. There is always water pooled up on both sides of the road.”
The layer of BX1200 Geogrid was covered with 36 in. of select embankment fill, followed by a second layer of BX1100 Geogrid . The construction crews completed the project with 12 in. of aggregate and 5 in. of asphalt paving.
More owners are selecting the Spectra System to:
- Simplify and speed up construction while increasing the performance of pavement surfaces;
- Decrease labor and equipment requirements;
- Reduce aggregate fill thickness;
- Reduce under cut and over-excavation requirements;
- Improve durability by spreading the applied load more evenly, reducing the pressure applied to the subgrade; and
- Enable construction to proceed even in difficult working conditions.