By: Terry Meier, Geofoam Specialist
It has been stated that an amateur sells products, a professional sells solutions to problems. One of the many problems that Geofoam solves is vertical load reduction on underground structures. The problem of earth pressure on deeply buried utilities has a great practical importance in constructing embankments over utilities.
EPS Geofoam blocks have been used for load reduction on buried utilities since 1988. The 100 to 1 weight ratio difference between conventional fill material and Geofoam brings about a significant load reduction on underground structures such as pipelines and culverts. In addition to its ultra-light weight advantage Geofoam has well defined compressibility characteristics which allow for controlled compression and yielding.
Geofoam also creates a compressive soft zone layer above the utilities. The soft zone (Geofoam) compresses more than the surrounding fill and thus induces positive arching above the utility. Earth pressure on deeply buried utilities is greatly affected by this arching effect. Arching diverts soil pressure away from the utility thus reducing expected vertical earth pressure.
A better understanding of the arching effect of EPS Geofoam on buried utilities has been obtained from field study full scale test measurements. Four instrumental field tests using Geofoam for load reduction on buried utilities were performed over a four year period. The Geofoam was placed above the utilities. Hydraulic pressure cells were placed at various locations above and adjacent to the utility to measure vertical and horizontal earth pressures.
Using Foam-Control® Geofoam was successful in reducing the vertical loads on the buried utilities. The average measured earth pressure above the crown of the utility ranged from 23% to 45% of the overburden pressure depending on the type of backfill which was used. Long term monitoring of the installations indicate no increased pressure on the buried utilities. Once again Foam-Control® EPS Geofoam is indeed a problem solver.