Pore-scale Modeling of Capillary Stress in Unsaturated Soil

本项目旨在提出一个孔隙尺度的微观力学模型框架，用于量化非饱和土壤中毛细管引起的晶间应力。重点是改进用于区分部分充满水的部分颗粒间液桥形式的孔隙网络和以饱和口袋形式完全充满水的部分孔隙网络的统计放大方法。相应的毛细管应力函数可以通过相对简单的土壤-水特征曲线测量来计算，在整个孔隙水饱和度范围内被量化，并被转化为饱和土壤行为的传统有效应力公式。具体目标是改进用于捕获广义孔几何形状的建模框架，解释细粒材料中的表面吸附效应，并解释干湿滞后效应。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的性能。旨在促进研究生和本科生研究、多样性和更有效地将非饱和土力学付诸实践的教育和推广活动与研究计划相结合。对控制非饱和土性状的孔隙尺度作用力和过程的基本了解有望使人们深入了解在非饱和土壤条件下可能出现的岩土工程实践中的问题，包括降雨诱发的滑坡、地基和开挖稳定性以及压实土方的动力响应。

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.