This section describes some of the more unique applications of EPS geofoam in construction activities in North America. Some of these special applications include noise or visual barriers, expansive soils, earthquake mitigation, permafrost and rockfall protection.
Noise and Vibration Damping
EPS geofoam can be used to build free-standing walls or embankments to reduce noise from highways. They can also be used to reduce the transmission of ground borne vibrations, for example, under railways or pavements, as part of the foundation of adjacent structures or as a cutoff wall between the railways or pavements and the adjacent structures.
EPS geofoam is available in a wide range of compressive resistances. Compressible applications utilize the compressibility of EPS geofoam to accommodate ground movements. In contrast to most applications where EPS geofoam is designed for loading below the compressive resistance at 1% of the EPS geofoam, compressible applications are designed for strains beyond 1%.
When properly designed, EPS geofoam, when in contact with expansive soils, deforms and reduces the stresses transmitted to the relatively stiff structures by allowing the soils to expand, compress the EPS geofoam and not impact the structure. This means that the retaining structure or floor slab, built adjacent to or on expansive soil, only has to be designed for a small percentage of the forces that would be expected due to swelling or heaving of the expansive soil.
EPS has two primary advantages that make it attractive for seismic design: its light weight and its compressibility. The low weight of EPS geofoam provides a significant reduction in the seismic forces imposed on buried structures, retaining walls, pipelines, etc., because the magnitude of the seismic force is proportional to the mass of the system, i.e., force equals mass times acceleration. Because EPS geofoam is moderately to highly compressible it can deform and act as a “buffer” to reduce the seismic energy imparted to the system. Numerical modeling of these buffer systems suggests that the horizontal seismic forces imparted to retaining walls and other buried structures can be reduced about 20 to 50%, depending on the thickness and compressive resistance of the EPS geofoam.
EPS geofoam embankments are stable during earthquakes based on post-earthquake performance observations from Japanese researchers. Other U.S. studies show that EPS geofoam embankments are inherently stable for small to moderate-size earthquakes. EPS geofoam has also been used atop and around buried steel pipelines to protect them from potential rupture during fault offset from a seismic event or other types of permanent ground displacement.
Roadways constructed over permafrost are susceptible to thaw settlement, which results in high maintenance costs and poor ride quality. The thaw settlement is caused by the permafrost thawing. The shoulders of the roadway tend to be the most problematic areas because there is less fill over the shoulders, which means less insulating material to prevent the heat from reaching the permafrost and causing thawing. Constructing an EPS geofoam embankment over the permafrost takes advantage of the insulating quality of EPS. The primary purpose of the EPS geofoam is to sufficiently insulate the underlying permafrost to minimize/prevent heat transfer into the frozen ground, which reduces thawing and thaw-consolidation of ice-rich permafrost soils to an acceptable level.
The light weight of EPS geofoam also induces little settlement due to increased stress even if the insulation effect of EPS geofoam does not keep the permafrost frozen. Finally, the ability to construct an embankment quickly and under adverse winter conditions is of great benefit in a climate with a short and unpredictable construction season.
Development in mountainous regions sometimes occurs where there is a high probability of rockfall. Structures, roads and railways built in the trajectory of the rock need to be protected. Protection galleries can be a good choice when the area to be protected is relatively narrow and limited, like roads and railways, and safety in the area below the protected area can be neglected. Traditionally, rockfall protection galleries are constructed with a soil layer over their cover, which provides limited energy absorption. Adding a layer of EPS geofoam under the soil cover could greatly improve the performance of the protection gallery due to the high energy absorption capacity shown by EPS geofoam as it strains during impact.