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TitlePermafrost geotechnical index property variation and its effect on thermal conductivity calculations
AuthorBrooks, H; Doré, G; Smith, S L
SourceCold Regions Science and Technology vol. 148, 2018 p. 63-76,
Alt SeriesNatural Resources Canada, Contribution Series 20170214
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories; Yukon; Alberta
NTS107; 106; 96; 95; 105I; 105P
AreaMackenzie River Valley
Lat/Long WENS-136.5000 -118.0000 69.0000 59.7500
Subjectssurficial geology/geomorphology; permafrost; boreholes; statistical methods; statistical analysis; coefficient of variation (COV); soil and ice classifications
Illustrationslocation maps; graphs; histograms; plots; tables
ProgramPermafrost, Climate Change Geoscience
AbstractGeotechnical borehole and sample data from three databases compiled by the Geological Survey of Canada were analyzed to determine the variability of geotechnical index properties within frozen soils. The analysis included 2662 boreholes with geological setting data, up to 60?m depth, within the Mackenzie Valley and Delta region of the Northwest Territories. A total of 7539 samples, each with soil and ice classifications and gravimetric moisture content data were included. Gravimetric and volumetric moisture contents were analyzed by general soil type to determine their coefficient of variation (COV) with depth and geologic setting. As expected, variability between geologic settings corresponded to the nature of the soil's depositional environment, and volumetric ice content variability decreased with increasing depth. General soil type was also used to determine the COV for dry density, specific gravity, and Atterberg limits for samples where testing was available. The variability of frozen thermal conductivities was estimated using Monte Carlo simulation and common equations from the literature based on the geotechnical index property variation. Recently-derived equations for thermal conductivity showed less variability compared to earlier methods.
Summary(Plain Language Summary, not published)
This paper utilizes information from over 2000 geotechnical boreholes in permafrost in the Mackenzie Valley NWT to characterize the statistical variability of various index properties for representative terrain types. Properties considered included grain size, moisture content and ground ice content. The results of this work were utilized to better define the thermal properties for various terrain types which can facilitate calculation of the range of thaw depths expected to occur due to climate variability and to define design values for infrastructure design. The results also support improved risk assessments and adaptation of infrastructure to changing permafrost conditions resulting from a changing climate.