Protection of Buried Utilities against Repeated Loading: Application of Geogrid-EPS Geofoam System

Abstract

Expanded polystyrene (EPS) geofoam is commonly used as lightweight fill materials in wide range of geotechnical engineering applications including protection of buried utilities and pipelines. EPS blocks are usually placed next to buried pipelines to reduce the overburden and traffic-induced pressure on them. In this paper, a new configuration of EPS blocks around the buried utility is defined and its performance under traffic loading examined. The proposed configuration consists of three buried EPS blocks. Two blocks (posts) are vertically oriented, while a capping EPS block (beam) is placed atop, leaving a void to protect the buried utility. Finally, soil cover is placed and compacted above the beam. By considering sufficient void space, the protection system will carry all the imposed load, and no stress will be incurred to the protected utility. The effects of beam thickness, soil cover thickness, EPS density, free span length between the posts, and soil cover reinforcement on the system's behavior under cyclic loading were explored through large-scale laboratory model tests. System performance enhanced when high-density EPS blocks, thicker beam and soil cover were used. The results also showed that reinforcing the soil cover with a single layer of geogrid could significantly lower the blocks' deformations and control their dynamic strain rate under cyclic loading. Finally, a three-dimensional finite-element model was developed, validated against experimental results, and used to gain more comprehensive insight into the protection system's performance under loading.