GeoSpec® Lightweight Fill Applications: Road Embankments

Roads placed over subsoil with low bearing capacity or with high settlement characteristics often settle to an unacceptable extent due to consolidation of the subsoil. These settlements are due to the weight of the road embankment imposing a load on the subsoil which it cannot sustain. If the road embankment is constructed out of GeoSpec lightweight fill material (geofoam) the load on the subsoil is much reduced and the settlement is reduced or eliminated.

Often poor soil conditions exist at rivers, muskegs or bogs where a bridge structure is supported on a firm foundation either directly or by piles. The road embankment is at increased depth due to the ground profile and the problem of soil settlement is emphasized.

Soils that have low bearing capacity or large settlement characteristics are soft clays with a high content of fines and water, non-cohesive soils (gravel, sand) with a high content of organic material and water, or any soil with a high content of organic material (peat is the worst example). With sufficient depth of these types of subsoil settlement can continue indefinitely as filling the road embankment to level it increases the load on the subsoil and the settlement continues.

Solutions to these settlement problems could include re-aligning the road to place it over firm ground. Alternatively, geotechnical engineers have long recognized the utility of using lightweight fill to reduce mass and associated gravitational driving forces.

Lightweight materials that have been used in embankment construction include chipped bark, sawdust, dried peat, fly ash, slag, cinders, cellular concrete, lightweight aggregates, expanded polystyrene geofoam (GeoSpec lightweight fill), shredded tires, and sea shells.

GeoSpec lightweight fill material is typically at least 50 times lighter than other types of lightweight fill materials (see table). To achieve a slope stabilization with a net reduction in driving mass of 100,000 kg (220,500 lb) within an soil slope embankment having an in-place soil density of 2100 kg/m3 (131 pcf) would require excavating and replacing soil with about 90 m3 (118 cy) of lightweight fill with a density of 1000 kg/m3 (62.5 pcf) or about 50 m3 (65.4 cy) of GeoSpec lightweight fill material of lightweight fill of 24 kg/m3 (1.5 pcf) density. GeoSpec lightweight fill can be used as a prefabricated fill in an area where it would be difficult to establish a compacted fill due to space limitations, adverse weather conditions, or site access

Properties of GeoSpec Lightweight Fill Material

Details regarding the material properties for GeoSpec lightweight fill material types offered are provided in the Technical Library. GeoSpec lightweight fill has different requirements from EPS insulation materials. The material properties provided in this section will provide general guidance for initial material selection.

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