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Using expanded polystyrene (EPS) geofoam in road and bridge projects

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Problem: Highway capacity is insufficient to meet growing demand

Traffic congestion on highways in the United States continues to be an area of concern to the traveling public, and to roadway managers. Every year, congestion continues to grow as vehicle travel increases and the nation’s bridges and roads deteriorate.

To help alleviate this growing congestion, capacity on U.S. highways and major roads must be expanded. In many circumstances, however, roadway embankment widening or new alignments may require construction over soft or loose soils that are incapable of supporting increased loads. Embankment construction projects must identify innovative materials and construction techniques to accelerate project schedules by reducing vertical stress on the underlying soil.

Solution: Get in, get out, and stay out with geofoam

Putting it in perspective:

  • 1 in every 5 highway projects is considered “traffic sensitive.”
  • 2 out of every 5 urban interstate miles are considered congested.
  • Traffic delays have more than tripled in the past 20 years.
  • By 2020, the U.S. population is expected to grow by 16% and vehicle travel is expected to increase by 42%.

Geofoam benefits:

  • Accelerates foundation construction, reduces project time line
  • Saves money
  • Requires limited labor for construction
  • Exerts little to no lateral load on retaining structure
  • Can be constructed easily in limited right-of-way areas and in adverse weather conditions

Successful applications: Results demonstrate geofoam advantages

Many states have used EPS geofoam in both large and small highway projects. By using geofoam as a lightweight fill, engineers at the Minnesota Department of Transportation (MnDOT) have realized significant time and cost savings for a number of small and moderate sized roadway embankment projects over deep, soft, organic soil deposits prevalent in the state.

After years of searching for a permanent solution to a failing slope problem on State Route 23A, New York State DOT turned to EPS geofoam. By replacing upper sections of the slide area, the state significantly reduced the driving forces that were causing the slide and successfully rehabilitated the roadway section.

Two large, high-profile jobs—the Big Dig in Massachusetts and Interstate-15 in Utah—turned to EPS geofoam to construct large embankment sections. Geofoam helped maintain the tight construction schedules that would not have allowed enough time for conventional embankment construction. Both projects illustrated the ease and speed with which EPS geofoam can be constructed for highway embankments.

Deployment Statement

This technology is a lightweight, rigid foam plastic that is approximately 100 times lighter than most soil, and at least 20 to 30 times lighter than other lightweight fill alternatives. This extreme difference in unit weight, compared to other materials, makes EPS geofoam an attractive fill material to significantly accelerate construction schedules.

Deployment Goal

By October 2008, EPS geofoam will be a routinely used lightweight fill alternative for state DOTs on projects where the construction schedule is of concern.

Deployment Status

EPS geofoam has been used on roadway projects in more than 20 states. The FHWA Resource Center has developed a half-day seminar on geofoam and has presented the seminar in 10 states. A guideline specification for state DOTs is being revised and updated to reflect trends in the industry and fluctuations in the cost of materials.

In addition, an innovations and advancements report is being prepared to highlight state-of-the-art developments in the use of geofoam as a lightweight fill material.

Source: U.S. Department of Transportation—Federal Highway Administration Resource Center

Kevin Dusenberry, associate vice president at DMJM Harris, and Ron Bygness, editor of Geosynthetics (formerly GFR), contributed to this article.

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