4.2         Geofoam Block Alignment

Generally, the cross section of a geofoam stabilized slope embankment contains layers of foam blocks, each layer being about 0.6m-0.83m thick. These layers rest on a leveling course of 0.15m thick sand or filter. The geofoam fill is usually capped with reinforced concrete slab of about 0.15m thickness. The concrete slab acts as a load distributing layer as well as a protection for the foam. The paving material and sub base layers are placed and compacted over the top of the concrete slab.

Two configurations for the distribution of foam blocks within the slope were studied. Figure 4-2 shows a configuration where the foam blocks are arranged such that the edge of the blocks nearest the face is inclined at an angle equivalent to that of the slope. The back edge of the geofoam configuration is vertical. In this case, the soil is either excavated to its normal angle of repose or supported with temporary sheeting while excavating and constructing the embankment. This arrangement may be required by specific projects or constraints. The vibratory driver for installation and withdrawn of the sheeting can trigger additional movement. The sheeting itself is expensive, making the geofoam solution less economical. Installation and the extraction of the sheeting is also time consuming. The advantage of a vertical back face with sheeting, though, is that the excavated space is less and the usable space during construction is more.

The configuration shown in figure 4-3 does not require sheeting. The shape of the foam back slope tends to be parallel to the repose angle of the soil.

A number of parameters can affect the factor of safety of a geofoam-stabilized slope. The characteristics of the soil such as its shear strength, density, and hydraulic conductivity constitute the most important factors. The geometry of the slope itself, such as height and inclination also affect the factor of safety. The geometry and position of the foam fill also control the factor of safety.

Figure 4‑1 Typical Cross Section of a Geofoam Stabilized Slope

Figure 4‑2 Arrangement of Geofoam Blocks with Two Inclined Edges