Project Profile: Idaho Bridge Expansion & Replacement

Topaz Bridge Expansion & Replacement  |  McCammon, Idaho  |  View Project Profile (pdf)

Idaho’s heavily used trucking route and bridge (circa 1940) expands from 2 to 4 lanes to increase safety and capacity using InsulFoam Geofoam.

Geofoam blocks were used to construct a new 500 foot long, 30 foot tall EPS block embankment.  The new embankment supports the US-30 road expansion and its approach to the new Topaz bridge - notably the longest span in the state of Idaho.

Geofoam blocks were used to construct a new 500 foot long, 30 foot tall EPS block embankment. The new embankment supports the US-30 road expansion and its approach to the new Topaz bridge – notably the longest span in the state of Idaho.

Topaz Bridge

The pavement section is constructed on top of the 45 foot tall combined soil & Geofoam block approach fill

Idaho Transportation Department’s first EPS Geofoam project was designed by Terracon Engineers and JUB Engineers of Boise.  EPS was specified as a soil replacing embankment fill material due to poor foundation soils and 2 steel fish culverts that could not bear the weight of traditional soil fill.  A new three-span, bridge replaced the existing bridge (from the 1940′s) crossing rail road tracks and expanding the highway to 4 instead of 2 lanes.  23,000 cubic yards of large block EPS was installed by Scarsella Brother Inc. and supplied by Insulfoam.

THE PROBLEM

The expansion of the US-30 and bridge replacement required a new fill embankment to support the new roadway and bridge approach on a very steep side slope.

The new (600 ft long) expanded bridge clears The Pontneuf River as well as the Union Pacific Railroad tracks, and required a new higher grade of both the bridge structure and the existing roadway to support the new wide and long center spans.

EPS

EPS block fill is partially installed, during bridge construction.

As a result the new bridge approach embankment would be 45-50 feet high, too costly to be retained by conventional concrete cantilever or MSE wall, and raised concerns about global stability.

Further challenges to the project design were the site conditions.  Located adjacent to the Portneuf River, shallow bedrock and loose or soft sediments underlie the new approach embankment.  This both challenged the new roadway embankment’s strength and stability, and limited deep foundation designs required with concrete walls.

THE EPS GEOFOAM FILL SOLUTION

To reach the new bridge’s approach embankment height of 45 feet, engineers chose a combined fill solution.  The lowest 15 feet was a small earthen embankment, while InsulFoam GF constituted the upper 30 feet.  4 1/2 feet of granular fill retained in wire gab ions and an asphalt pavement section were installed directly on top of the EPS blocks to complete the full height of the new embankment.

Custom fabricated "tongs" grip the large EPS blocks without damaging them.

Custom fabricated “tongs” grip the large EPS blocks without damaging them.

The exposed vertical face of the EPS is eventually covered with a protective shotcrete facing.

The exposed vertical face of the EPS is eventually covered with a protective shotcrete facing.

 

 

 

 

 

 

 

 

 

The soft sediments underlying the site required the lower earthen embankment to settle (80 days), but the InsulFoam GF block fill required no additional surcharge time or secondary compaction by the contractor.  Traffic moved on the existing roadway throughout the installation of the upper embankment, which was a key factor for the expansion to finish when weather conditions permitted.

Net

Near “Net-Zero” surcharge loads.  The void in between the blocks and the native slope was filled with sand.

The ultra lightweight nature of EPS allowed the total design weight of the tall embankment to be week under the bearing capacity of the poor foundation soils which aided ITD in successfully completing their first EPS Geofoam project.

Geofoam Lightweight Geo-synthetic Fill:

  • Soft Soil Remediation
  • Lateral Load Reduction
  • Slope Stabilization
  • Buried Utility Protection
  • Structural Void Fill
  • Predictable Elastic Modulus
  • Exceptional Strength & Stability
  • Exceeds 75 year Design Life
  • Weather, Insect & Mold Resistant
  • 100% Recyclable

 

MORE GEOFOAM SOLUTIONS IN HIGHWAY CONSTRUCTION

View Project Profile (pdf)

Geofoam Saves Time, Money During Three Projects

Originally posted on Better Roads Magazine

I-80 / I-65 Interchange, Gary, Indiana

I-80 / I-65 Interchange, Gary, Indiana

The Federal Highway Administration (FHWA) has promoted the use of expanded polystyrene (EPS) geofoam as a lightweight embankment soil alternative for a number of years.  In a 2006 report, the agency’s Technical Service Team described the material as a “field-tested, budget-friendly winner.”  Why?  FHWA engineers list the following benefits:

  • Accelerated construction
  • Payroll, transportation and equipment cost savings
  • Reduced labor time for construction
  • Exerts little or no lateral load on retaining structures
  • Easily constructed in limited right-of-way situations
  • Allows application in adverse weather conditions.
Trinidad

Trinidad

The material is approximately 100 times lighter than soil, which save time.  Additionally, a single truck can carry approximately 120 cubic yards of goefoam versus 12 dump truck loads needed for an equivalent volume of earthen fill.  This reduces hauling costs, both in fuel and labor.  Geofoam is easy to install by hand, so it reduces expenses for heavy equipment.

Following is a discussion of tangible benefits derived from geofoam usage in real-world applications such as:

I-80 / I-65 interchange, Gary, Indiana:  FHWA recommended a net-zero load methodology for the roadbed to prevent post-construction settlement.

To reduce the amount of excavation of the high-organic content soils, the contractor, Walsh Construction, used EPS geofoam blocks.  A six-member crew installed 700 cubic yards of geofoam in one week working four- to five-hour days. The geofoam was delivered to the job site on 32 flatbed truckloads, whereas traditional fills would have required more than 400 dump trucks in the highly congested project area leading into and out of metro Chicago.

Highway Interchange, Valsayn, Trinidad:  The project team for an interchange between Trinidad’s Churchill-Roosevelt Highway (CRH) and Uriah Butler Highway (UBH), the island nation’s primary highways, used an EPS geofoam sub-base to solve an engineering challenge and save time in the process.

Highway geometry required placing new lanes adjacent to both sides of an existing fly-over ramp’s support pier. The grade for the lanes required placement of about 10 feet of embankment fill on top of the pier’s pile cap. Engineers determined that traditional fills would have caused unacceptable settlement of the compressive layers located below the fill.

To build the embankment while keeping loads down on the pile cap, Vinci Construction Grands Projets specified EPS geofoam as a lightweight fill, which provided an alternative to building a concrete slab founded on piles to support the load from the road and transfer it away from the pier pile cap. No heavy equipment was needed for the fill placement, as crews were able to install the geofoam blocks by hand.

The geofoam resulted in lower and smoother post-construction differential settlements of the roadway in both the transversal and longitudinal directions. It also eliminated the need for additional geotechnical investigation for potential additional piles. The ability to place the EPS geofoam during the rainy season was crucial to keeping the project on schedule. Crews placed 2,100 cubic yards of EPS geofoam in only 3.5 days.

Lake Cataouatche Pump Station Bridge, New Orleans, Louisiana:  The U.S. Army Corps of Engineers used EPS geofoam when it needed to build a service bridge over above-ground outlet pipes at the Lake Cataouatche pump station near New Orleans.

The bridge abutments are over extremely soft soil (compressible peat). A traditional soil embankment would have added substantial load to the underlying soils. To minimize loads on the soft soils, the project team used EPS geofoam under the bridge abutments.

Final thoughts

In addition to being lightweight, EPS geofoam has predictable elastic behavior and will not decompose. Further, unlike other lightweight fills such as shredded tires or wood chips, EPS geofoam blocks are homogenous, which provides uniform load transfer and eliminates differential settlement. All of these factors combine to make the material an ideal choice in many road sub-base applications at the federal, state and local levels.