Unsaturated soil mechanics & near-ground-surface phenomena

非饱和土力学

• 批准号: 3787-2008
• 负责人: Fredlund, Delwyn
• 金额: $ 4.37万
• 依托单位: University of Saskatchewan
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2008
• 资助国家: 加拿大
• 起止时间: 2008-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=388843
• 关键词: Unsaturated; soil; mechanics; near; ground

There were two primary subjects that have been historically been by-passed in textbooks on classical soil mechanics; namely, the behavior of unsaturated soils and the quantification of moisture flux conditions at ground surface. The last 40 years have witnessed rapid strides in our understanding of unsaturated soil mechanics as it applies to relatively homogeneous continua. There are; however, two aspects of unsaturated soil mechanics that stand in great need of further research. The first aspect involves the structural characterization of the soil conditions near ground surface. Often these soils contain extensive fissures, fractures and cracks that significantly affect the unsaturated soil properties. It is proposed that the secondary macrostructure of these soils be characterized through use of bimodal mathematical functions. It is proposed that there be one air entry value associated with the macrostructures features and another air entry value associated with the intact matrix of the soil. The unsaturated soils near to the ground surface thus become bimodal, nonlinear and hysteretic. Many of these soils also exhibit significant volume change during wetting and drying. The second aspect of unsaturated soil mechanics in need of research is the quantification of moisture flow conditions at the ground surface. Both the infiltration of water and the exfiltration during evaporation (as well as evapotranspiration) are subject areas of great interest to practicing geotechnical engineers. These conditions are closely related to our understanding of the impact of climate change. It is through the ability to mathematically quantify water balance conditions at the ground surface that the effects of climate change can be taken into consideration through numerical modeling studies. In my estimation, the characterization of fissured, fractured and cracked soil masses near the ground surface, and the quantification of ground surface moisture flux conditions are two of the main topics requiring further research in unsaturated soil mechanics.

经典土力学教科书中历史上忽略了两个主要主题：即非饱和土壤的行为和地表水分通量条件的量化。过去 40 年，我们对非饱和土力学的理解取得了快速进步，因为它适用于相对均匀的连续体。有;然而，非饱和土力学的两个方面非常需要进一步研究。第一个方面涉及地表附近土壤状况的结构特征。这些土壤通常含有广泛的裂缝、裂缝和裂纹，严重影响非饱和土壤的性质。建议通过使用双峰数学函数来表征这些土壤的次级宏观结构。建议存在一个与宏观结构特征相关的空气进入值和另一个与完整土壤基质相关的空气进入值。因此，靠近地表的非饱和土变得双峰、非线性和滞后。许多这些土壤在湿润和干燥过程中也表现出显着的体积变化。非饱和土力学需要研究的第二个方面是地表水分流条件的量化。水的渗透和蒸发（以及蒸散）过程中的渗出都是岩土工程师非常感兴趣的主题领域。这些条件与我们对气候变化影响的认识密切相关。通过对地表水平衡条件进行数学量化的能力，可以通过数值模拟研究考虑气候变化的影响。据我估计，地表附近裂隙、破裂和开裂土体的表征以及地表水分通量条件的量化是非饱和土力学需要进一步研究的两个主要课题。