Date of Award

12-2025

Document Type

Thesis

Degree Name

Master of Science (MS)

Degree Statement

Master of Science in Geophysics

Department

Department of Geosciences

Granting Institution

University of Alaska Fairbanks

Committee Chair

Nicolsky, Dmitry

Committee Member

Romanovsky, Vladimir

Committee Member

Bray, Matt

Committee Member

Babcock, Esther

Committee Member

Grapenthin, Ronni

Committee Member

Hazen, Beez

Table of Contents

Chapter 1: Introduction.

1.1 Background

1.2 Utilidors

1.3 Comparative review of arctic utilidor systems

1.4 Utilidor in Utqiaġvik

1.5 Research problem

Chapter 2: Observations and methodology.

2.1 Thermistor sensor background

2.2 Thermistor sensor quality control

Chapter 3: Numerical model.

3.1 Governing equations and assumptions

Chapter 4: Model simulation of actual conditions.

4.1 Background

4.2 Model geometry

4.3 Geometric mesh

4.4 Validation of numerical platform

4.5 Mesh resolution sensitivity analysis, convergence criteria, and precision effects

4.6 Material and climate properties

4.5 Additional model assumptions and limitations

Chapter 5: Numerical results

5.1 Climate calibration

5.2 Model geometry reevaluation and modification

5.3 Deeper model calibration

Chapter 6: Sensitivity analysis.

6.1 Purpose and approach

6.2 Results and observations

6.3 Interpretation and implications

Chapter 7: Case study.

7.1 Warmer climate

7.2 Methodology

7.3 Climatology analysis

7.4 Interpretation

7.5 Warming scenarios - relationship between ground temperature and degree days

7.6 Recommendations for maintaining permafrost stability

Chapter 8: Discussion, conclusions, and recommendations.

8.1 Summary of findings

8.2 Broader interpretations

8.3 Contributions to the field

8.4 Study limitations

8.5 Recommendation for future work

8.6 Conclusions

References.

Abstract

Permafrost degradation in Arctic regions poses increasing risks to infrastructure as climate warming accelerates thaw processes, alters hydrology, and deepens the active layer. In Utqiaġvik, Alaska, utilidors— utility conduits—play a vital role in protecting water and wastewater services, yet their thermal performance under changing conditions remains poorly constrained. This thesis evaluates the thermal behavior of the Site U-1 direct buried pipes on Stevenson Street using historical thermistor resistance data converted to temperature, combined with calibrated two- dimensional TEMP/W numerical models. The models incorporate layered backfill materials and polyurethane insulation, while also simulating operational influences of water and wastewater temperatures. Calibration was conducted through sensitivity analyses of soil thermal conductivities, fluid temperatures, and geometry modifications, with performance assessed using root mean square error (RMSE), mean absolute error (MAE), and seasonal bias relative to in situ measurements. Results show that ground temperature variability is strongly influenced by soil stratigraphy and pipe operation. Certain adjustments—such as increasing silty sand and slurry conductivities by 20% or raising wastewater temperatures by 1 °C—improved alignment with measured data. Overall, this work demonstrates the iterative nature of model calibration and provides new insight into direct buried pipes-ground interactions in permafrost terrain. Findings have broader implications for assessing infrastructure vulnerability, informing retrofitting strategies, and guiding the design of more resilient utility systems in Arctic communities facing rapid environmental change.

Download

Share

COinS