Altering the thermal regime of soils below heated buildings in the continuous and discontinuous permafrost zones of Alaska

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Author
Perreault, Paul Vincent
Chair
Shur, Yuri
Committee
Hulsey, J. Leroy
Barnes, David
Ahn, Il Sang
Metadata
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URI
http://hdl.handle.net/11122/6636
Abstract
This research investigates the impacts of thermal insulation on the thermal regime of soils below heated buildings in seasonally and perennially frozen soils. The research provides practical answers (A) for designing frost‐protected shallow foundations in unfrozen soils of the discontinuous permafrost zone in Alaska and (B) shows that applying seasonal thermal insulation can reduce the risk of permafrost thawing under buildings with open crawl spaces, even in warming climatic conditions. At seasonal frost sites, this research extends frost‐protected shallow foundation applications by providing design suggestions that account for colder Interior Alaska’s air freezing indices down to 4 400 °C∙d (8,000 °F∙d). This research includes field studies at six Fairbanks sites, mathematical analyses, and finite element modeling. An appendix includes frost‐protected shallow foundation design recommendations. Pivotal findings include the discovery of more pronounced impacts from horizontal frost heaving forces than are likely in warmer climates. At permafrost sites, this research investigates the application of manufactured thermal insulation to buildings with open crawl spaces as a method to preserve soils in the frozen state. This research reports the findings from using insulation to reduce permafrost temperature, and increase the bearing capacity of permafrost soils. Findings include the differing thermal results of applying insulation on the ground surface in an open crawl space either permanently (i.e., left in place), or seasonally (i.e., applied in warm months and removed in cold months). Research includes fieldwork in Fairbanks, and finite element analyses for Fairbanks, Kotzebue, and Barrow. Pivotal findings show that seasonal thermal insulation effectively cools the permafrost. By contrast, Fairbanks, Kotzebue, and Barrow investigations show that permanently applied thermal insulation decreases the active layer, while also increasing (not decreasing) the permafrost temperature. Using seasonal thermal insulation, in a controlled manner, satisfactorily alters the thermal regime of soils below heated buildings and provides additional foundation alternatives for arctic buildings.
Description
Dissertation (Ph.D.) University of Alaska Fairbanks, 2016
Table of Contents
Chapter 1: General Introduction -- 1.1 Investigating Practical Insulation Methods for Arctic Soils -- 1.2 One Hypothesis, Two Parts, Different Applications -- 1.2.1 Part A. Seasonal frost sites – directed heat confinement to keep footing soils thawed -- 1.2.2 Part B. Permafrost sites – restricting summer heat gain to keep soils cold -- 1.3 Investigation Methods for Both Parts -- Chapter 2: General Background for Both Parts -- 2.1 Forces in Frost Susceptible Soils -- 2.1.1 Basal freezing pressures -- 2.1.2 Tangential freezing stresses -- 2.2 Air Freezing Index -- 2.3 Geothermal Heat Flux -- Part A. Frost protected shallow foundations – for seasonal frost sites -- Chapter 3: Frost‐Protected Shallow Foundations -- 3.1 Introduction and Literature Review -- 3.2 Field Studies, Six Sites in the Seasonal Frost Zone -- 3.2.1 Insulation types and long‐term effective thermal resistivity -- 3.2.2 Six field locations -- 3.2.3 Monitoring methods -- 3.2.4 Field results and discussions -- 3.2.4.1 Timberland results and discussion -- 3.2.4.2 Merlin results and discussion -- 3.2.4.3 Goshawk results and discussion -- 3.2.4.4 Violin results and discussion -- 3.2.4.5 Bonita results and discussion -- 3.2.4.6 Army results and discussion -- 3.3 Conformal Mapping Analysis, Results and Discussion -- 3.4 Finite Element Modeling -- 3.4.1 Software program -- 3.4.2 Boundary conditions -- 3.4.3 Material properties -- 3.4.4 Modeling results and discussion -- 3.5 General Discussion for Frost‐Protected Shallow Foundations in Interior Alaska -- 3.5.1 Freezing isotherm shape is vertical and deep -- 3.5.3 Insulation discussion -- 3.5.4 Thermistor and temperature readout discussion -- 3.5.5 Field monitoring considerations -- 3.5.6 Other frost protected shallow foundation considerations -- 3.6 Part A – Pivotal Findings for Frost‐Protected Shallow Foundations in Interior Alaska -- 3.6.1 Using frost‐protected shallow foundation systems requires some cautions -- 3.6.2 Recommendations -- 3.6.3 Summary, frost‐protected shallow foundations for non‐permafrost sites in cold climate -- Part B. Permafrost protection – by restricting summer heat gain -- Chapter 4: Insulation Methods for Permafrost Zone -- 4.1 Introduction and Literature Review -- 4.1.1 Building distress concerns with warmer climates -- 4.1.2 Temperature dependent adfreeze bond may be unrepairable if broken -- 4.1.3 History and insulation methods for Arctic foundations -- 4.1.4 Current arctic foundation design methods -- 4.2 Analyses Without Buildings, Permafrost Zone -- 4.2.1 Means and methods for testing permafrost sites without buildings -- 4.2.1.1 Finite‐element thermal analyses -- 4.2.1.2 Boundary conditions -- 4.2.1.3 Current climate temperature input -- 4.2.1.4 Surface temperature adjustments (“n‐factors”) -- 4.2.1.5 Analyses startups and run times -- 4.2.2 Results for permafrost sites without buildings -- 4.2.2.1 Fairbanks -- 4.2.2.2 Kotzebue -- 4.2.2.3 Barrow -- 4.3 Analyses with Buildings in Place, Permafrost Zone -- 4.3.1 Means and methods for testing permafrost sites with buildings in place -- 4.3.2 Field study, one site, Willow House -- 4.3.3 Field study, results and discussion -- 4.3.3.1 Site work, thermistor discussion -- 4.3.3.2 Site work, insulation discussion -- 4.3.4 Thermal analyses by finite‐element program -- 4.3.5 Print screen results, Fairbanks -- 4.3.6 Graphic results and discussion for Fairbanks -- 4.3.6.1 Comparative results, center of building with edge of building -- 4.3.6.2 Comparative results, permanent or seasonal insulation, with or without snow -- 4.3.6.3 Fairbanks discussion -- 4.3.7 Graphic results and discussion for Kotzebue -- 4.3.8 Graphic results and discussion for Barrow -- 4.4 Climate Change Impacts -- 4.4.1 Testing means and methods for climate change -- 4.4.2 Results and discussion for changed climate -- 4.4.3 Important caution -- 4.5 Discussion, Multiple Investigations, Permafrost Protection via Thermal Insulation -- 4.5.1 Variability in n‐factors not investigated -- 4.5.2 Snow drifting not investigated -- 4.5.2 Insulation reduces surface thermal amplitude and reduces active layer depth -- 4.5.3 Possible additional usage for shallow footings founded on permafrost -- 4.5.4 Research considerations and uncertainties -- 4.6 Part B – Pivotal Findings for Permafrost Sites -- 4.6.1 Results and recommendations, permafrost sites, permanent thermal insulation -- 4.6.2 Results and recommendations, permafrost sites, seasonal thermal insulation -- 4.6.3 Results and recommendations, permafrost concerns for warming climate -- 4.6.4 Results and recommendations, open crawl space and snow removal -- 4.6.5 Summary, thermal insulation methods for permafrost sites -- Chapter 5: Conclusions -- 5.1 Frost‐Protected Shallow Foundations – for Seasonal Frost Sites -- 5.2 Seasonal Frost Sites – Pivotal Findings -- 5.3 Permafrost Protection ─ Summary -- 5.4 Permafrost Sites ─ Pivotal Findings -- 5.5 Future Studies -- References.
Date
2016-05
Type
Dissertation
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