| dc.description.abstract | This report presents a comprehensive overview of field investigations and large-scale plate loading tests conducted at the UNIS East site in Longyearbyen from March 2020 to July 2023. These tests were undertaken as part of the NUNATARYUK project, with a primary focus on studying the long-term behaviour of frozen soil in response to temperature change and permafrost degradation. The significance of this study and report lies in their contribution to the assessment of climate change impacts on permafrost regions, particularly with respect to infrastructure stability. The design of the long-term plate loading test was based on a systematic site investigation carried out under the NGTS (Norwegian Geo-Test Sites) project. The design encompassed natural permafrost sampling, laboratory testing, back calculation of test results, and the establishment of a meticulously organized setup for continuous long-term monitoring and data collection. The test conducted at Longyearbyen, Norway, where the ground in a large part of the city is Holocene marine deposits. The active layer thickness in the region was approximately 1 to 2 meters. Sampling was conducted at depths of 4 to 6 meters in boreholes located approximately 1 meter from the plate loading test site. Three footing plates, with 300 mm diameter each, were placed on saline clay permafrost at around 4.2 m depth. An equilateral triangle steel frame with an edge length around 4 m is supported by these three legs and used for a loading platform though adding concrete blocks as dead weight. A stepwise loading procedure was adapted to monitor the long-term creep settlements. The experimental results and field measurements reveal that the mechanical implications of a warming climate extend beyond the typical melting point, impacting the frozen soil several degrees below that temperature. Ground subsidence initiates through a creep deformation in the warming frozen soil, several degrees below the melting point, which is then followed by an accelerated deformity caused by thawing settlement as temperatures approach the melting point. The observations suggest that creep deformation may contribute significantly to the overall subsidence phenomenon. In addition to the direct insights gained from these tests regarding the long-term behaviour of frozen soil in response to temperature changes, it’s imperative to highlight its significance as benchmark problem for verifying and refining computational models and simulations. The data and observations collected during this extensive study provide valuable reference points for developing and testing predictive models. Such models are essential for assessing the impacts of climate change on permafrost regions and their associated infrastructures. | |
