Development of Micromechanically-Based Models for Unsaturated Geomaterials

非饱和岩土材料微力学模型的开发

• 批准号: RGPIN-2016-04086
• 负责人: Wan, Richard
• 金额: $ 2.62万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=668048
• 关键词: Development; Micromechanically; Based; Models; Unsaturated

Emerging geomechanics problems associated with infrastructure, energy and the environment present challenges to basic tenets of geotechnical engineering. For instance, unsaturated, thermal and coupled conditions demand analyses that go beyond traditional theories which are mostly phenomenological in nature. Unsaturation in the simplest case refers to the presence of more than one fluid, e.g. liquid and gas separated by interfaces within the pore space. This results in the behaviour of an unsaturated medium being vastly different from the dry or fully saturated case. In fact, unsaturation confers the medium with an apparent cohesion, a higher strength and stiffness that are a function of moisture and temperature. This gain in strength is evanescent under varying hydraulic and thermal loads such as climatic fluctuations or gassy conditions. As such, strength could be rapidly lost causing spontaneous collapse failures in geostructures.***The overall goal of this research is to pursue a more fundamentally scientific study of unsaturated conditions in geomaterials as multiphasic systems. This will be accomplished by exploring the various scales down to the particle and pore scales, including the water menisci. Our understanding of unsaturated media will be extended by recognizing new phenomena key to the improvement of design in engineering practice in terms of judgement, quality and safety. The adopted approach is multiscale, probing into the nature of the pressures exerted by the individual phases, including interfaces separating them, on particles that are in mutual contact through mechanical forces. An important aspect will be to elucidate the role of interfacial tension that exists within interfaces on multiphase flow, as well as the strength, deformation and failure characteristics of unsaturated geomaterials.***The proposed research mathematically examines force transport in a heterogeneous random granular assembly with particles connected by discrete liquid menisci as a representative elementary volume. As such, stress contributions from the various phases, including the interfaces, can be worked out through a homogenization scheme knowing the statistics of the grain packing and liquid bridges. This will elucidate many well-known processes driven by interfacial tension such as capillary or suction stresses as a function of saturation. In contrast to previous work, the analysis will encompass the spatial distribution of liquid menisci, fabric anisotropy of solid skeleton, temperature, and identify an effective stress that controls strength and deformations. Besides determining the various components of the stress tensor in an unsaturated medium, the associated strain tensor will also be derived following an energy approach.***Applications of this research include toxic waste disposals, contaminant transport in porous media, and CO2 injection in geological formations.**

与基础设施、能源和环境相关的新兴地质力学问题对岩土工程的基本原则提出了挑战。例如，不饱和，热和耦合条件的分析要求超越传统的理论，主要是现象学的性质。在最简单的情况下，不饱和是指存在多于一种流体，例如通过孔隙空间内的界面分离的液体和气体。这导致了非饱和介质的行为与干燥或完全饱和的情况有很大的不同。事实上，不饱和度赋予介质表观内聚性、更高的强度和刚度，其是水分和温度的函数。这种强度的增加在变化的水力和热负荷下，如气候波动或气体条件下，是短暂的。因此，强度可能会迅速丧失，导致地质结构的自发坍塌故障。这项研究的总体目标是追求一个更根本的科学研究地质材料的非饱和条件作为多相系统。这将通过探索各种尺度下到颗粒和孔隙尺度，包括水的渗透来实现。我们对非饱和介质的理解将通过认识新现象来扩展，这些新现象是在判断、质量和安全方面改进工程实践设计的关键。所采用的方法是多尺度的，探讨由各个相施加的压力的性质，包括分离它们的界面，通过机械力相互接触的颗粒。一个重要的方面将是阐明多相流界面内存在的界面张力的作用，以及非饱和岩土材料的强度，变形和破坏特性。建议的研究数学上检查力传输在一个异质随机颗粒组装与离散液体颗粒作为一个代表性的基本体积连接的颗粒。因此，应力的贡献，从各个阶段，包括接口，可以通过一个均匀化计划知道的统计数据的颗粒包装和液体桥。这将阐明许多众所周知的过程驱动的界面张力，如毛细管或吸力应力作为饱和度的函数。与以前的工作相比，分析将包括液体的空间分布，固体骨架的结构各向异性，温度，并确定控制强度和变形的有效应力。除了确定非饱和介质中应力张量的各个分量外，还将按照能量方法推导出相关的应变张量。*这项研究的应用包括有毒废物的处理，多孔介质中的污染物传输，以及地质构造中的CO2注入。