Peer reviewed publications:

• Birhan, A., and Negussey, D. Effects of confinement on the stress strain behavior of EPS geofoam. International Conference on Geotechnical Engineering, Shanghai, China, 2014.
• Birhan, A., and Negussey, D. Effect of Confinement on Creep Behavior of EPS Geofoam, ASTM Geotechnical Journal, 2014 (accepted for publication).
• Negussey, D., Singh, S., Liu, C. and Andrews, L., Investigation of a Large Culvert Reconstruction Failure, Transportation Research Record, (in review for possible presentation and publication in January 2015 @ the TRB annual meeting in Washington DC).

The I88 crossing of Carrs Creek in Delaware County, NY was washed out during record flooding in 2006. Two persons were killed and the roadway was closed for traffic. A new pre-cast concrete culvert was rapidly constructed using geofoam and compacted soil backfill. Shortly after construction, excessive settlements developed in the geofoam and all of the backfill was sub-excavated and replaced with lightweight expanded shale. A large number of unconfined compression tests were performed on exhumed geofoam samples at different laboratories in a follow up investigation. The test results indicated the geofoam initial modulus was lower than indicated in ASTM D 6817 for the specified grade of geofoam. The study identified the noted inferior geofoam quality to be the likely cause for the excessive settlements. The relatively rigid culvert, compressible geofoam and compacted soil constitute conditions of soil structure interaction. This proposal is for detailed study of the geofoam failure through selected laboratory tests, computer modeling and simulation to provide a better understanding of the main causes and mechanisms that contributed to the failure. The investigation will feature selected laboratory tests on geofoam of the same grade and also on exhumed samples that have acquired a stress history. Stress induced anisotropy and confining stress effects on geofoam strength and modulus will be examined. A geofoam inclusion within the backfill can offer significant advantages. Because of its low density, the weight of the backfill on the culvert will become less. The relatively high compressibility of geofoam would facilitate differential movement and arching effects. Depending on the type of arching and extent of induced trench conditions that develop, loadings on culverts can be significantly reduced. This can lead to use of standard culvert sections under high fills to enable cost savings and rapid construction. The research will investigate these effects in the geofoam failure considering the construction sequence and installation details. As part of the deliverables, the geofoam failure will be re-designed optimizing the amount and location of the geofoam within the backfill and considering extreme flood levels and potential for uplift due to buoyancy. The adequacy of the specification and alternative uses for the exhumed geofoam stockpile will be considered.