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Investigating movement and characteristics of a frozen debris lobe, south-central Brooks Range, Alaska

Abstract

Frozen debris lobes (FDLs) are large masses of soil, rock, incorporated organic material, and ice moving down permafrost-affected slopes. In this paper, we focus on FDL-A in the south-central Brooks Range, Alaska, which is an impending geohazard to the Dalton Highway, located just under 40 m away from the highway embankment. We present the results of multi-faceted research, including field-based studies, laboratory testing of soil samples, slope stability analysis, and a geographic information system (GIS) analysis. Subsurface instrumentation indicates that major movement of FDL-A occurs in a shear zone 20.6 to 22.8 m below the ground surface, with temperature-dependent internal flow as a secondary movement mechanism. Surface measurements show an overall average rate of movement of 1.2 cm per day, which is an increase over historic rates. The slope stability analysis required a back analysis to determine soil strength parameters at failure, resulting in cohesion values between 43 and 53 kPa and friction angles between 10 degrees and 16 degrees . The modeling results indicated a high sensitivity to pore-water pressure and cohesion. This is critical since the melting of massive ice and thawing of frozen soil will increase pore-water pressure and lower shear strength, resulting in the acceleration of FDL-A towards the Dalton Highway. The GIS analysis also provided insight into the movement and instability of FDL-A and provided groundwork for a GIS protocol for examining catchment and lobe features of all FDLs along the highway corridor.


ISSN: 1078-7275
EISSN: 1558-9161
Coden: ENGEA9
Serial Title: Environmental & Engineering Geoscience
Serial Volume: 22
Serial Issue: 3
Title: Investigating movement and characteristics of a frozen debris lobe, south-central Brooks Range, Alaska
Affiliation: University of Alaska at Fairbanks, Fairbanks, AK, United States
Pages: 259-277
Published: 201608
Text Language: English
Publisher: Geological Society of America, Association of Engineering Geologists, College Station, TX, United States
References: 49
Accession Number: 2017-006338
Categories: Engineering geologyGeomorphology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch maps
N67°47'60" - N67°49'00", W149°49'60" - W149°46'60"
Secondary Affiliation: Alaska Department of Natural Resources, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201705
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