One of the major technical challenges in constructing natural gas pipeline is how to cope with cold region pipeline engineering aspects caused by freezing and thawing of soil around the pipeline. A pipeline running through discontinuous permafrost is subject to the potential risk of an unacceptable deformation, which is caused by thaw settlement or frost heaving at the boundary of permafrost and non-permafrost. It is important for a design engineer to predict the behavior of soil-pipeline interaction and make an adequate assessment of safety of pipeline in such portion. Although extensive efforts have been made to document those aspects, relatively little research has been carried out to comprehensively study the behavior of pipeline in response to short- and long-term change of thermal and mechanical properties of permafrost. In order to understand the complex behavior of natural gas pipeline and surrounding soil in cold regions, a full-scale experimental gas pipeline was constructed near Fairbanks, Alaska and had been studied intensively. The research project was carried out from the year of 1999 to 2004 under the sponsorship of Japan Science and Technology. The changes of ground thermal regime, vertical movement of the pipeline and the induced bending stress in the pipes were studied. The research team including researchers from Japan and the U.S collected and analyzed the field measurements from the test site. In this paper, the major findings and lessons learned from the project will be presented together with the result of numerical simulations related to the experiment.

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