Pore-scale Modeling of Capillary Stress in Unsaturated Soil

该项目旨在推进一个孔隙尺度微力学建模框架，用于量化非饱和土壤中毛细血管诱导的粒间应力。重点是改进一种统计升级方法，用于区分部分孔隙网络以颗粒间液体桥的形式部分充满水，部分孔隙网络以饱和袋的形式完全充满水。相应的毛细管应力函数可以从相对简单的土-水特征曲线测量中计算出来，在孔隙水饱和度的整个范围内进行量化，并将其转化为饱和土壤特性的常规有效应力公式。具体目标是完善建模框架，以捕获广义孔隙几何形状，考虑细颗粒材料的表面吸附效应，并考虑干湿滞后效应。保水行为、颗粒和孔隙形态、剪切强度、拉伸强度和小应变动态行为的实验室测量将用于评估模型的性能。旨在激发研究生和本科生的研究、多样性和更有效地将非饱和土力学应用于实践的教育和推广活动与研究计划相结合。提高对孔隙尺度力和过程的基本理解，控制非饱和土的行为，有望产生对非饱和土条件下可能发生的岩土工程实践问题的见解，包括降水诱发的滑坡，基础和开挖稳定性，以及压实土方工程的动态响应。

This project seeks to advance a pore-scale micromechanical modeling framework for quantifying capillary-induced intergranular stress in unsaturated soils. Focus is placed on refining a statistical upscaling methodology used to differentiate portions of the pore network partially filled with water in the form of interparticle liquid bridges and portions of the pore network completely filled with water in the form of saturated pockets. A corresponding capillary stress function may be computed from relatively simple measurements of the soil-water characteristic curve, quantified over the complete range of pore water saturation, and cast into conventional effective stress formulations for saturated soil behavior. Specific objectives are to refine the modeling framework for capturing generalized pore geometries, account for surface adsorption effects in fine-grained materials, and account for wetting-drying hysteresis effects. Laboratory measurements of water retention behavior, particle and pore morphology, shear strength, tensile strength, and small-strain dynamic behavior will be used to evaluate the model performance. Education and outreach activities designed to stimulate graduate and undergraduate research, diversity, and more effective implementation of unsaturated soil mechanics into practice are integrated with the research plan. Improved basic understanding of the pore-scale forces and processes that govern unsaturated soil behavior is expected to yield insight into problems in geotechnical engineering practice that may occur under unsaturated soil conditions, including precipitation-induced landsliding, foundation and excavation stability, and the dynamic response of compacted earthworks.