Considering the need to undertake pipeline replacement in a cost-effective manner while ensuring the public safety interest, evaluating the performance of pipelines subject to soil loading from landslides is a key concern in some of the natural gas distribution systems operated by FortisBC Inc. As it is typically uneconomical and impractical to relieve stresses in distribution pipe systems by excavating or instrumenting the pipelines to measure the highly localized strains, undertaking numerical and/or analytical modeling combined with experimentation is a key aspect in attempting to relate the measured ground movement to performance of pipe. For this purpose, capturing the fundamental soil-pipe interaction in small-diameter extensible plastic pipes and undertaking field monitoring to validate the numerical model are critically important. With this background, this paper presents field measurement and numerical modeling undertaken to model the performance of 115 mm diameter medium density polyethylene (MDPE) pipes buried in West Quesnel, BC, Canada. Using field survey data, the active landslides occurring perpendicular to the pipe axis at these two sites have been periodically characterized since 2000/2001.

Materials removed from the pipe system were tested to characterize the pipeline material behavior and limit strains. The data derived from these tests along with a range of soil behaviors are used to support pipe-soil interaction numerical simulation and thus characterize the strains accumulated in the pipeline in service. This paper discusses the limitations, challenges and recommendations for numerical modeling of soil-pipe interaction in small-diameter plastic pipes.

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