Use of EPS Bedding Materials in Pipeline Installation

Pipeline construction in open trenches requires an appropriate degree of compaction of the soil around and below the springline, and especially in the haunches area, to ensure embedment on the contact surface of the trench. However, due to the lack of space in many inner-city areas with large numbers of different pipes crossing each other, it can sometimes be difficult in practice to carry out a proper soil compaction in accordance with regulations. This in turn may lead to damage, not only to the newly installed pipe but also to surrounding pipes. There are various innovative materials available to effectively provide proper embedment, and one cost-effective alternative is the use of expandable polystyrol (EPS) bedding materials. These prefabricated sections of hard foam are specially tailored to fit different types of pipe. They substitute for soil in the haunches area to ensure an optimized degree of embedment. In addition, it is possible to install two pipes on top of each other using EPS, which greatly reduces the amount of excavated soil required for backfill. The lightweight construction also simplifies handling on site. This paper presents an examination of the state-of-the-art on the use of EPS bedding materials in pipeline installation, focusing on their mechanical properties, quality control and durability against chemical, physical, and biological environmental impacts. The long-term behavior of installed EPS materials and the possibility of their use on several construction sites are assessed. In addition, using finite-element calculations, stress and deformation of installed EPS material with particular regard to creeping and buoyancy effects are investigated. Finally, the results from the product tests, experimental results and calculations, together with recommendations for their practical application are presented.