Demand for higher grade linepipe that can help reduce the total cost of long-distance gas pipelines has increased recently. As a result, pipelines using high-strength linepipes such as Grades X70 and X80 have been planned in hostile environments such as landslide-prone mountain areas, reclaimed land where liquefaction is an issue and polar regions where frost heave occurs. Buried pipelines in these regions are expected to be subjected to large deformation due to the large ground movement caused by these geohazards. It is not possible to apply conventional stress-based design in cases where the longitudinal stress of pipe material greatly...