Highway 48 (Mankato, MN)
Cracks in bridge threaten railway
Year Completed: 2010
During construction of a multi-year, $25 million road project in Blue Earth County on CSAH 12, an embankment leading to a bridge failed, temporarily affecting service on the DM&E Railroad's mainline that runs along the base of the embankment.
Following soil borings, testing of four potential fill materials, and cost considerations, Gale Tec Engineering Inc. determined that TDA (Tire Derived Aggregate) was the best choice for solving this civil engineering challenge. In addition to being the least expensive option, shredded tires are about one-third the weight of regular soil and possess shear strength that prevents slides.
The lightweight property of the shredded tires, placed on top of the existing soft soils, reduced the pressure that could increase the possibility of future slope failure. The TDA's ability to interlock when compacted during installation increases the strength of the slope, providing additional support and safety.
More than 16,000 cubic yards of tire shreds (about 820,000 tires) were used in this bridge embankment project. Rather than occupying landfill space, these recycled tires are providing multiple public benefits: cost savings, increased safety and an expected reduction in long term maintenance costs on this portion of the roadway.
Following completion of the project, Blue Earth County was recognized by Governor Dayton for “creative engineering solutions” and its partnership with First State Tire Recycling in resolving this problem.