Pore-scale Modeling of Capillary Stress in Unsaturated Soil

本计画旨在提出一个孔隙尺度的细观力学模型架构，以量化非饱和土壤中毛细作用所引起的粒间应力。重点放在完善的统计放大方法，用于区分部分的孔隙网络部分填充水的形式的颗粒间液体桥和部分的孔隙网络完全填充水的形式的饱和口袋。相应的毛管应力函数可以从土壤-水特征曲线的相对简单的测量值计算，在孔隙水饱和度的整个范围内量化，并转换为饱和土壤行为的常规有效应力公式。具体目标是完善的建模框架，捕捉广义孔的几何形状，考虑在细颗粒材料的表面吸附效应，并考虑湿-干滞后效应。将使用保水行为、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来评估模型性能。教育和推广活动，旨在刺激研究生和本科生的研究，多样性，更有效地实施非饱和土力学的实践与研究计划相结合。提高孔隙尺度的力量和过程，治理非饱和土的行为的基本理解，预计产生洞察岩土工程实践中可能发生的问题，在非饱和土条件下，包括降水引起的滑坡，基础和开挖的稳定性，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.