Slope Movement in Permafrost near Fairbanks, Alaska

Document Type

Conference Proceeding

Publication Date

8-11-2016

Department

Department of Civil, Environmental, and Geospatial Engineering

Abstract

A section of oil pipeline near Fairbanks, Alaska is experiencing hillslope movement. While the pipeline’s support system was designed to handle large movements, the slope movements are starting to exceed the anticipated design requirements. The pipeline was constructed on low angle permafrost slopes composed of Fairbanks silt. The silt occurs in three relatively distinct layers; an upper active layer, followed by an ice-rich silt layer overlying a non-ice rich silt layer. Based on inclinometer data, the slope movement is occurring near the ice-rich layer/non-ice layer interface at a rate of 4.5 cm/year. A traditional slope stability back analysis indicates that for slope instability to develop, the ice-rich layer (assumed the weakest) would require the layer’s friction angle to be in the range of about three degrees; much lower than traditional strength values would suggest. While some small underground gold mine shafts are located about 100 meter from the base of the slope movement, it is speculated that an additional factor causing slope creep is the syngenetic formation of the permafrost, which formed in successive frozen layers during freezing. Recent research has also suggest the possibility of cold weather neoformation of smectic clays developing that could assist in slope creep.

Publication Title

Geo-Chicago 2016

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