Pore Pressure Response to Loading of Warm Permafrost

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The research focuses on enhancing Canadian permafrost engineers' understanding of the factors that control both stability of shallow slopes and deformation behavior of near surface foundations in permafrost regions. The temperature of this near surface permafrost is gradually warming due to climate change, and this warming is impacting the strength and deformation behavior of this near surface permafrost. This warming can lead to detrimental behavior of these materials related to stability of slopes and deformation of foundations. The research will establish the controlling influence of internally generated pore water pressure in partially frozen soils on the strength and deformation of this warming permafrost. Climate change has its major impact on the near surface frozen material at and just beneath the permafrost table (below the active layer). The ice rich composition of this warm permafrost is a challenge for the design engineer when evaluating their stability. Significant amounts of unfrozen water at below freezing temperatures can exist in warm permafrost, and the amount of this water increases with a small increase in temperature. Warming allows ice to change phase in the pore space, and this water can result in increases in internal pore water pressures in the partially frozen material. These changing pore water pressures can reduce the effective stresses, thus leading to a decrease in the resistance to sliding of the warming permafrost. The research is focused on determining how these pore pressures can change and measuring these changes with both temperature and stress. Understanding how these pore pressures develop will allow use of the effectives stress principle in future analysis of warm permafrost. This concept has not been used to date because of a lack of being able to accurately predict the internal pore water pressures in partially frozen soils. Research will also be carried out on the behavior of the pore water pressure developed during advancement of the freezing front in soils. This is being undertaken to improve the profession's understanding of the fundamentals of frost heave and the impact of rate of freezing advancement that control the amount of heave. The research findings will reduce the near term and future costs of road and airport foundations, and foundations and stability of slopes adjacent to this infrastructure.