Thermo-Hydraulic-Mechanical Properties of Frozen and Thawing Soils

北部占加拿大陆地面积的40%。朝鲜拥有世界级的矿产、石油和天然气储量，是一个拥有巨大经济机会的地方。朝鲜的可持续资源开发需要设计和建造通道、挡水结构、管道、采矿设施、港口、机场和建筑物等基础设施。北方也处于气候变化影响和适应的前沿。强有力的环境保护是可持续发展的重要组成部分，特别是在永久冻土环境中。如果充分了解冻融效应并使其适应气候变化趋势，则可提供充分的保护。本研究计划解决了几个问题：•二维或三维环境中的解冻固结；•富冰土壤在温度高于-1℃时的蠕变行为；•解冻材料的抗剪强度和边坡稳定性。Morgenstern和Nixon（1971）用一维公式和固有简化的分析技术研究了融化固结过程。他们的分析表明，融化土壤中的孔隙压力分布与融化固结比R有关，R是一个耦合融化速率和从融化前沿排水速率的参数。主要的假设是，在解冻完成之前，解冻的土壤不会沉降。毋庸置疑，在富含冰的土壤中，融化沉降率高达70%，在分析过程中忽略沉降会导致设计过于保守。本研究建议使用现代计算工具来推导一个解决方案，其中的过程是完全耦合的。柔性pde将允许在一、二或三维环境中将解冻土壤中的排水、解冻锋的传播和巩固与表面的移动边界耦合起来。将建立新的孔隙压力图，并提出分析具体问题（地基、道路、管道和土坝、融化边坡的边坡稳定性）的方法。-1℃以上富冰土的蠕变特性冻土受到荷载作用时，会产生瞬时变形和随时间变化的变形。速率效应与温度和应力有关，并随冻土中存在的冰量而变化。在文献中，人们发现冻土的大量数据温度低于-1°C。然而，考虑到每百年几度的气候变化，需要对温度高于-1°C的富冰土壤进行更多的研究。这对于冰透镜与倾斜地面平行形成的斜坡来说尤其重要。这些斜坡可能显示出高达2米/年的蠕变速率，与瑞士阿尔卑斯山冰川的行为相同。实验室测试将在控制在特定温度变化小于0.05℃的环境室中进行，以获得蠕变参数和本构方程。Flex-PDE将用于研究斜坡和其他结构在高温下使用参数的行为。本研究还将探讨融化土的抗剪强度与孔压耗散程度之间的关系。可获得的数据很少，需要在解冻期间进行充分的设计，以确保在永久冻土上建造的结构的稳定性。

The North is forty percent of Canada’s land mass. With world-class mineral, oil and gas deposits, the North is a place of tremendous economic opportunity. Sustainable resource development in the North requires to design and build infrastructures such as access roads, water retaining structures, pipelines, mining installations, ports, airports and buildings. The North is also on the front line of climate change impacts and adaptation. Strong environmental protection is an essential component of sustainable development, especially in a permafrost environment. Adequate protection is provided if the freeze-thaw effects are well understood and adapted to the climate change trends. This research proposal addresses several issues: • Thaw-consolidation in a two of three dimensional environment; • Creep behaviour of ice-rich soils at temperatures higher than -1 °C; • Shear strength of thawed materials and slope stability. Thaw-consolidation Morgenstern and Nixon (1971) have studied the thaw-consolidation process in a one-dimensional formulation and using analytical techniques with its inherent simplifications. Their analysis showed that the pore pressure distribution in the thawed soil can be related to the thaw-consolidation ratio, R, which is a parameter coupling thaw rate and rate of water drainage away from the thaw front. The main assumption was that the thawed soil did not settle until thaw was complete. Needless to say that thaw settlements van reach up to 70% in ice rich soils and neglecting settlement during the analysis leads to overly conservative design. This research proposal uses modern computing tools to derive a solution in which the processes are fully coupled. Flex-PDE will allow to couple drainage in the thawed soil, thaw front propagation and consolidation with a moving boundary at the surface in one, two or three dimensional environments. New pore pressure charts will be established and a methodology for analysis specific problems (foundations, roads, pipelines and earth dams, slope stability in thawing slopes) will be proposed. Creep behaviour of ice-rich soils at temperatures higher than -1°C When a frozen soil is subjected to a load, it will respond with an instantaneous deformation and a time-dependent deformation. The rate effects are temperature- and stress-dependent and vary with the amount of ice present in the frozen soil. In the literature one finds a significant amount of data for frozen soils are temperature lower than -1°C. However, considering a climatic change of several degrees per hundred years, more study need to be conducted for ice-rich soils at temperatures higher than -1°C. This is particularly important for the case of slopes in which ice lenses have formed parallel to the sloping ground. These slopes may display creep rates as high as 2m/year, identically to the behaviour of glaciers in the Swiss Alps. Laboratory tests will be conducted in environmental chambers controlled to a specific temperature with a variation of less than 0.05°C in order to obtain creep parameters and constitutive equations. Flex-PDE will be used to study the behaviour of slopes and other structure using the parameters at high temperatures. Shear strength of thawed soils The proposed research will also investigate the relationship between shear strength and degree of pore pressure dissipation in thawing soils. Little data is available and is needed for adequate design during thaw for ensuring stability of structures built on permafrost.