Coupled thermo-geophysical inversion for permafrost monitoring
This dissertation summarizes results of 5 years of field, laboratory and modeling studies of permafrost properties in Ilulissat, West Greenland. Ilulissat town and airport are located in an area of frost-susceptible, ice-rich marine sediments with residual salinity content in pore water, which effec...
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| Format: | Book |
| Language: | English |
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Technical University of Denmark, Department of Civil Engineering
2018
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| Online Access: | https://orbit.dtu.dk/en/publications/d578dc27-0740-49e2-9148-27744f35de55 https://backend.orbit.dtu.dk/ws/files/145164684/PhD_thesis_Sona_Tomaskovicova_Final.pdf |
| Summary: | This dissertation summarizes results of 5 years of field, laboratory and modeling studies of permafrost properties in Ilulissat, West Greenland. Ilulissat town and airport are located in an area of frost-susceptible, ice-rich marine sediments with residual salinity content in pore water, which effectively lowers the freezing point of the soil. Consequently, these sediments have strength properties similar to thawed ground in spite of ground temperatures well below 0 ◦C. In the view of increasing pressure on infrastructure development, better knowledge of such permafrost types, distribution, thermal and geotechnical properties is needed for informing sound and sustainable design choices. Monitoring approaches using geophysical methods have become more widespread in permafrost studies, as they are indicative of spatial variation and in-situ processes rather than isolated properties in time and space. However, they only provide indirect information about the properties in question. To enable quantitative interpretation of in terms of thermal properties and ground ice changes, there is a need for extensive calibration and validation data. In this project, we experimented with use of time lapse geoelectrical data for calibration of thermal model simulating heat transfer in active layer and permafrost. To acquire necessary calibration/validation data, we built a station for monitoring of ground temperature, electrical resistivity and soil moisture regimes. Automated resistivity measuring system was optimized for time lapse acquisitions in this environment characterized by extremely variable electrode grounding conditions between thawed vs. frozen season. Dense data series collected over three years provided insight into relationships between soil petro-physical parameters. We observed that temperature-dependent ground physical properties depend strongly on history of freeze-thaw cycles. Magnitudes of observed water content and resistivity hysteresis respectively have implications for thermal modeling and ... |
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