June 27, 2014
Project Description
During construction of a multi-year, $25 million road project in Blue Earth County on CSAH 12, a 30 foot embankment leading to a bridge began cracking longitudinally [Gale, Lichty, and Forsberg, 2013], temporarily affecting service on the DM&E Railroad's mainline that runs along the base of the embankment. County Engineer Al Forsberg, consulted with Gale -Tec Engineering Inc. to evaluate the situation. Data from borings identified a soft clay and peat soil problem which likely caused the slope distress. It was determined reconstruction of the embankment was required to prevent a future embankment failure [Scrap Tire News, 2012].
Project Goals
In order to stop the embankment from sliding, Gale-Tec analyzed various options to correct the situation. When it was determined the installation of a shear key would require difficult excavation, engineers chose to use a light weight fill strategy. Three potential fills were analyzed for their ability to solve the problem in a cost-effective manner, including expanded polystyrene (EPS) blocks, light weight aggregate and shredded tire material. It was determined shredded tires were the most cost effective choice to provide an acceptable slope stability factor [Gale,
Lichty, and Forsberg, 2013].
Figure 1. Note soft organic soils at bottom of the embankment, overlay deeper peat material, next to the rail line. Installation of lightweight TDA embankment is visible in this photo.
According to Gale, “Shredded tires have a high interface friction angle and low weight, about one-third of the weight of regular soil.” [Scrap Tire News, 2012]. The light weight property of the shredded tires, placed on top of the existing soft soils, reduced the pressure that could increase future slope failure. A high interface friction angle occurs when tire pieces interlock during compaction in the installation process.
Installation of Tire Derived Aggregate
Approximately 16,000 cubic yards (12,230 cubic meters) of single pass tire shreds (the equivalent of
480.000 tires) were used to reconstruct the embankment. To install the shredded tires, a layer of geotextile was laid out and an excavator placed the shredded tires in three foot lifts on top of it.
Geotextile was used to separate soil and tire shreds. Next, the equipment operator compacted each lift with a large tracked vehicle (dozer). To achieve compaction on top of the geotextile, the operator ran across the top of the tire fill until less than one inch of compression was observed.

After all lifts were installed, the geotextile fabric was pulled over the top of the shredded tires and overlapped to encapsulate the fill.
Finally, three feet of common embankment cover was placed on top of the tire shreds and compacted [Gale,
Lichty, and Forsberg,
2013]
Figure 2. Shredded tires are seen on top of the geotextile layer as they were being placed in the embankment.
Project Outcome
Following reconstruction of the embankment, Blue Earth
County indicated the problem had been solved. [Scrap Tire
News, 2012]. Project engineers later reported that "The completed embankment, the adjacent bridge wing wall and the adjacent rail road tracks have experienced no visual signs of distress since completion. The pavement over the shredded tire fill has also experienced no noticeable distress [Gale, Lichty, and
Forsberg, 2013].
The county was recognized by
Figure 3. After compaction, the geotextile fabric was pulled over the tire shreds and 3 feet (1 m) of soil was placed on top of the embankment fill to provide additional compression of the tire shreds.
Governor Mark Dayton for “creative engineering solutions” and its partnership with First State Tire

Recycling, the company providing the shredded tire material (tire derived aggregate) for the project
[Dayton, 2012].
Additional Benefits from the Project
About 480,000 tires were used in the bridge embankment project [Gale, Lichty, and Forsberg, 2013].
Rather than occupying landfill space or fostering mosquito habitat, these recycled tires are providing multiple public benefits-cost savings, increased safety and an expected reduction in long term maintenance costs on this bridge site.
Product Manufacturer
First State Tire Recycling, located in Isanti, MN, produces a line of shredded tire material called Green
Aggregate Fill. Currently, this line contains two size ranges of shredded tires (also called tire derived aggregate). Its larger sized tire shred, R.-T.E.A., was used in this project. The company has produced and distributed shredded tire material to more than 200 projects for over 25 years in the state of Minnesota and surrounding areas [First State Tire Recycling, 2014].
References
Dayton, M. (October 12, 2012). Certificate of Recognition. Presented to Blue Earth County Board of
Commissioners.
First State Tire Recycling. (Isanti, MN: “Green Aggregate Fill: R.-T.E.A. and More”,
http://www.firststatetire.com/svc-rtea.html)
Gale, S., Lichty, N., and Forsberg, A. (2013). “Bridge Approach Embankment Slope Distress: Analysis,
Monitoring, Design & Remediation - A Case Study”. Geo-Congress 2013: pp. 1384-1399. doi:
10.1061/9780784412787.139
Scrap Tire News. “TDA Rescues Failing Road Project”, http://www.scraptirenews.com/blog.php
(Leesburg, VA: Recycling Research Institute, January, 2012).