Geotechnical Study and Alternatives Analysis for an LNG Storage Tank in Fairbanks, Alaska

摘要

Since 2012, site geotechnical studies have been performed for the development of an LNG storage tank in Fairbanks including the design of several foundation alternatives. The geotechnical effort was phased and included subsurface studies of several potential tank locations and at the existing LNG facility, observations related to prior construction impacts on warm permafrost soils, and shear wave velocity profiling for seismic hazard analyses. In addition to the subsurface studies, a scaled pile load test was performed to better understand the potential pile performance in warm permafrost for a heavily loaded structure. LNG storage tanks are designed to maintain internal temperatures of -160°C, and heaters are installed in thawed soil to avoid the development of permafrost below the LNG storage tanks. Typically, large LNG storage tanks on permafrost soils have been supported on deep foundations with elevated pile caps to provide separation between the storage tanks and ground to avoid aggrading permafrost and associated basal frost heave below the tanks. Because of the seismic demand at the site, a foundation system with a thermal break became very expensive. Several alternatives were considered to maintain permafrost at the site.