| Description |
Questar Corporation commissioned and funded this research, in partnership with the University of Utah and Bechtel Corporation, to develop methods of protecting steel natural gas pipelines crossing zones of permanent ground deformation. The goal of this research was the development and testing of an Expanded Polystyrene (EPS) Geofoam cover system for such pipelines across active faults or areas of permanent ground deformation (e.g., landslides, permafrost thaw, liquefaction-induced lateral spread). The goal of an EPS Geofoam cover system atop a buried pipeline is to reduce the lateral, longitudinal and vertical forces induced on the pipe as the surrounding ground undergoes permanent deformation. The properties of EPS Geofoam have distinct advantages that lead to improved pipe performance during large ground deformation. The most important of these are its low unit weight and relatively high compressibility. These advantages are the primary focus of this research. Further, the interaction of a pipe and EPS Geofoam was explored and analyzed in a loading case where the pipe was pushed directly into the EPS. In addition to laboratory-scale tests, full-scale tests were conducted with vertical and horizontal plane strain movement of pipe interacting with EPS Geofoam cover systems. Subsequently, numerical modeling was done of the field tests to further evaluate the use of an EPS cover system for applications experiencing large, permanent deformation. The results of the research program have shown that EPS Geofoam can be used as a cover system for steel pipelines crossings at active normal faults, or for other types of permanent ground deformation where the expected offset is predominately vertical. |
