Pore Pressure Response to Loading of Warm Permafrost

该研究的重点是加强加拿大多年冻土区工程师对控制浅层边坡稳定性和近地表基础变形行为的因素的理解。由于气候变化，近地表永久冻土的温度正在逐渐变暖，这种变暖正在影响近地表永久冻土的强度和变形行为。这种变暖会导致这些材料的不利行为，与斜坡的稳定性和基础的变形有关。本研究将建立部分冻土内生孔隙水压力对暖化多年冻土强度和变形的控制影响。气候变化对永久冻土层及其下方（活土层以下）的近地表冻结物质有重大影响。在评估这些温暖的永久冻土的稳定性时，富含冰的成分对设计工程师来说是一个挑战。大量低于冰点温度的未冻水可以存在于温暖的永久冻土中，并且这些水的数量随着温度的小幅升高而增加。变暖使冰在孔隙空间中改变相，而这种水会导致部分冻结材料内部孔隙水压力的增加。孔隙水压力的变化可以降低有效应力，从而导致变暖的永久冻土的滑动阻力降低。研究的重点是确定这些孔隙压力如何变化，并测量这些变化随温度和应力的变化。了解这些孔隙压力是如何发展的，将有助于在未来对温暖永久冻土的分析中使用有效应力原理。由于缺乏对部分冻土内部孔隙水压力的准确预测，这一概念至今尚未得到应用。研究冻结锋推进过程中土体孔隙水压力的变化规律。这是为了提高专业人员对冻胀基本原理的理解，以及控制冻胀量的冻结进度的影响。研究结果将减少近期和未来道路和机场地基的成本，以及邻近基础设施的地基和斜坡的稳定性。

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.