In 2010, the Mississippi Department of Transportation made plans to widen existing bridges and shoulders on I-59 in Laurel, Mississippi.
The challenge? "We had a limited amount of right of way and we didn't have time to go buy more. Really what we were trying to do was find a way to limit our footprint so that wherever we corrected our slopes on the shoulders to meet the current standards, they didn't fall outside of the right of way," explained Brent Quick, District Area Engineer for the Mississippi DOT at the Laurel project office.
With these parameters in mind, the DOT set out to find a solution that would limit excavation. "That's where the retaining walls came in," Quick explained. "The walls allowed us to correct the slopes on the shoulders without going outside of the right of way."
The DOT had used Redi-Rock on previous projects and Redi-Rock was also on their approved products list. "The DOT recognized the advantage of minimized excavation with Redi-Rock, especially for this project," explained Jason Sailers of Piedmont Precast, the local Redi-Rock manufacturer and retailer. The massive size of each Redi-Rock block allows tall gravity walls to be built without the need for reinforcement in many applications. Even taller reinforced walls are possible.
The project included a total of 12 separate Redi-Rock walls totaling roughly 60,000 square feet (5,574.2 square meters). To put that in perspective, that's over 20,000,000 pounds (9,071,847.4 kilograms) of concrete! The walls ranged in height from 10 feet (3 meters) tall to 25 feet (7.6 meters) tall.
The largest wall was 10,000 square feet (929 square meters) and was built as a gravity structure (no geogrid required).The base of the gravity wall was built using Redi-Rock 60 inch (1520 millimeter) base blocks which weight as much as a Chevy Corvette. The rest of the wall was built using Redi-Rock 41 inch (1030 millimeter) blocks which weigh as much as a Budweiser Clydesdale. The advantages of gravity walls include minimized excavation as well as minimized installation time - both of which were important for this project.
The rest of the walls were reinforced using geogrid. Even though minimizing excavation was one of the primary objectives of the project, engineers were able to design reinforced walls using Redi-Rock that still fell within the right of way requirements.
A great benefit of the Redi-Rock system is that gravity and reinforced walls have the same aesthetic stone face, making it impossible to tell the difference between a gravity and reinforced wall once they're installed.
The project was installed over the course of one year by the General Contractor on the project, Tanner Construction. The walls were backfilled using 57 stone and manufactured sand. On top of the walls, concrete swales direct water to the sides of the walls to prevent erosion.
The DOT chose Redi-Rock's Cobblestone texture for the project. Although aesthetics weren't a primary concern, "I like the way it looks," Quick said. "The walls do the job that we were looking for."
Redi-Rock has been used on DOT projects in multiple states and provinces. Contact your local manufacturer to see how Redi-Rock has been used in your area!
Project: I-59 S Curve Project #139 Owner: Mississippi DOT Block Manufacturer: Piedmont Precast Engineer: Engineered Earth Solutions; Mississippi DOT Engineering Offices Installer: Tanner Construction Company, Inc. Location: Laurel, Mississippi Year Built: 2010-2011