ESCS Used as Backfill Reduces Load on Culvert

By Big River Industries, Inc.

Designers of a major interchange under construction just north of Birmingham, Alabama had an engineering challenge. New traffic lanes needed to go over the top of an existing concrete drainage system. The problem? The volume of fill material needed to build the area up to grade was enough to cause concerns about cracking the culvert.

Presently known as “Corridor X”, the 169-million dollar project is being built by Archer-Western Contractors of Atlanta. The addition of two newCulvert traffic lanes posed a challenge to designers at the Alabama Department of Transportation. Portions of the new roadway will travel over an existing 2,500 foot concrete drainage system that is twenty feet underground.

“The box culvert ends up being pretty deep and it would take a significant amount of fill material to get it back up to grade,” said Jeff Speck, VP of Sales and Marketing for Big River Industries. “If you backfill with ordinary soil and fill material, those loads would be high enough to cause concerns about over-stressing and cracking the box culvert.”

ESCS lightweight aggregate manufactured by Big River Industries provided a solution. Contractors backfilled three excavated areas with over fifteen thousand cubic yards of ESCS. “To reduce the weight as much as possible, they placed the ESCS without adding water,” said Speck.

Protecting a concrete pipe or culvert from being damaged is a new application for Big River. “This is only the second project of this type we have done where we’ve supplied lightweight aggregate for fill over the top of a pipe that’s buried deep beneath the highway. It’s a great application for ESCS because it reduces the load on that pipe or box culvert by more than half compared to normal weight material,” said Speck. “The reason ESCS is so good in that application is its very low density, and a very high angle of internal friction. Because you have a very low density and a very high friction angle, the pressure is greatly reduced.”

The product used in this geotechnical application was manufactured at Big River’s Livingston, Alabama plant. It was loaded at the facility’s distribution center and delivered by multiple trucks to the jobsite about two hours north of the plant. After two weeks of placement, the culvert is once again deep underground. Eventually, traffic will travel over the area never aware of the issue designers had to solve to make the new lanes possible.

“This project is yet another example of how ESCS lightweight aggregate provides a solution for a unique engineering challenge. The properties of ESCS are so much different from ordinary fill materials that it allows engineers to come up with a solution to solve some real tough challenges,” said Speck.

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