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How Well Can We Predict Changes in Ground Temperatures Using FEA Methods?

Explore the questions designers should ask and the predictions of ground temperature changes in warm and degraded permafrost using FEA methods. Discusses ambient temperatures, freezing and thawing indices, snow depths, and the use of climate data in design cases.

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How Well Can We Predict Changes in Ground Temperatures Using FEA Methods?

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  1. What Questions Should Designers Ask? Does it Matter if the Project is in Warm or Cold Permafrost? Degrading or Degraded Permafrost? Beez Hazen, Northern Engineering & Scientific, Anchorage, Alaska (beez@northern-engineering.com) How Well Can We Predict Changes in Ground Temperatures Using FEA Methods?

  2. Look at Predictions for Two, Hypothetical Projects: One in Warm Permafrost in the Copper River Basin plus discussion of climate data for this project -- how it has varied, how we have used it One in Western Alaska, Degraded Permafrost Short Discussion on projects in the High Arctic

  3. Copper River Basin, Alaska

  4. Ambient Temperatures, Copper River Basin (Gulkana FAA)

  5. Ambient Temperatures Seem to Be Warming, But are They Warming During Winter and Summer by Equal Measure? Thawing and Freezing Indices

  6. Calculation of Freezing and Thawing Indices (Where Freezing Index is calculated using data from Fall one year through Spring the next)

  7. Gulkana Freezing and Thawing Indices

  8. Another Example: Kuparuk Freezing and Thawing Indices

  9. Another Example: Bethel Freezing and Thawing Indices

  10. Gulkana Snow Depths

  11. Gulkana Snow Depth Index (feet * days)

  12. Gulkana Windspeeds

  13. Full-surface Energy Balance Model (needs data from Class 1 NOAA recording station) ambient temperatures windspeeds cloud cover and emissivity surface roughness surface absorptivity and emissivity snow depths, density, thermal conductivity evapotranspiration Nfactor Model ambient temperatures snow depths, density, thermal conductivity thawing and freezing Nfactor (as function of temperature) snow thermal conductivity (as function of time, etc.) Passive and/or Active Refrigeration ambient temperature and windspeeds Use of the Climate Data

  14. 4’ Thick Gravel Pad Built Upon Warm (Degrading) Permafrost 10” Thermal Pile with 16’ Diameter by 2” Thick Insulation Skirt Axisymmetric Model Four Cases: 1: Design Case w/ 0.09F/year Warming 2: Just Long-Term Average Ambient (else identical to Design) 3: 200% Snow Depths (else identical to design) 4: 50% Snow Depths (else identical to design) All same initial conditions, same soils, same everything except climate TQUEST Predictions For 4 Cases

  15. Compare: Design Case w/ 0.09 F/year Warming With: Prediction Using Long-Term Average Temperatures (no Ramp) __________________________________________________________________ Quick, Month-by-Month Predictions for 10 years. Simulations Start Early March. Year-by-Year Predictions For Early October (about maximum active layer) until Year 35 Predicted Temperature Contours

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