Utilizing Geofoam in Foundation Design for Steep Sloped Lots

Foundation Design Layout

Foundation Design Layout

A custom high end home was built on a very steep hillside lot overlooking Lake Washington near Seattle.  The owner of this home owns an excavation/gravel business.  He has all of the heavy equipment and free soil he could ever want, yet he chose to backfill three foundation walls with geofoam.  This project was originally designed with a compacted soil backfilled MSE wall that would have to be trucked down 95′, through a country club and from the top of the hill.  The amount of concrete, reinforcement, tie backs and forming costs that were removed from the foundation design more than paid for the geofoam and reduced the total weight of the import fill material by over 2 million pounds.

 

Geofoam Installation, Lake Washington Residence

Geofoam Installation, Lake Washington Residence

Benefits that lead to overall project cost savings by using geofoam as an alternative to traditional soil fill:

  • Geofoam is easily installed and the lightweight nature of geofoam allows it to be maneuvered by hand and used on projects with tight construction access where the use of larger mechanical equipment may not be feasible.
  • Shotcrete, Gunite, or soil can be placed directly against geofoam eliminating the need for expensive forming.
  • Construction traffic and import costs are minimized, as 1 flatbed truck of geofoam is equivalent to approximately 12 dump truck loads of traditional fill.
  • Congestion on the roads or road closures leading in and out of a project site is minimized.
  • The construction time of a project is reduced as several feet of geofoam can be placed in a fraction of the time that it would take to the place and compact traditional soil fill in the required 8 to 12-inch lifts.  As an added incentive, geofoam does not require compaction testing like tradition fill.
  • Decreased maintenance costs as a result of less settlement issues from the low density geofoam.
  • Tight construction scheduling can easily be maintained using geofoam as it can be installed during any type of weather or site conditions.
  • Geofoam is extremely eco-friendly and geofoam blocks can be re-used in other projects or be recycled.
Geofoam Installation, Lake Washington Residence

Geofoam Installation, Lake Washington Residence

Geofoam Installation, Lake Washington Residence

Geofoam Installation, Lake Washington Residence

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.

Reducing Loads for Soft Soil Remediation

Geofoam Installation, Phillis Wheatley Elementary

Geofoam Installation, Phillis Wheatley Elementary

Built in 1954, Phillis Wheatley Elementary School in New Orleans has been closed since Hurricane Katrina flooded the area and was left in a state of disrepair.  The 57 year old school was originally built as a segregated school for African Americans and was decided to be demolished and rebuilt after much opposition, debate and protests.  Demolition was completed in 2011 and the new school is in construction.

InsulFoam Geofoam was chosen as a lightweight fill to raise the main slab from its original elevation and lighten up loads on the subsoils.  Geofoam’s lighweight nature takes up space without adding stress to the underlying soil or structure.  There are many benefits of using InsulFoam Geofoam for reducing loads for soft soil remediation such as:  INCREASES speed of installation and productivity, DECREASES rights-of-way concerns, traffic closures, heavy equipment costs, soil removal costs, borrow-fill placement, ELIMINATES surcharging time/cost, soil settlement, and secondary compaction.

InsulFoam Geofoam is also environmentally friendly and 100% recyclable, containing no HCFCs or formaldehyde. With superior stability and long-term R-value, InsulFoam Geofoam resists insects, mold, decomposition and severe weather conditions, including freeze-thaw cycles and moisture penetration.

CLICK HERE to see Phillis Wheatley Elementary GEOFOAM construction installation photos

Phillis Wheatley Elementary, Geofoam Installation

Geofoam Installation, Phillis Wheatley Elementary

Phillis Wheatley Elementary

Geofoam questions or need to discuss your project?

Contact Nico Sutmoller, Geofoam Specialist

nico.sutmoller@insulfoam.com

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