Collaborative Research: Experimental and Computational Investigation of Multiphase Consolidation for Partially Saturated Soils

部分饱和土壤是一种三相土材料，在固体颗粒之间的空隙中含有空气和水。这种土壤通常在各种土木工程的现场施工中遇到，包括地基、垃圾填埋场、斜坡、挡土墙、压实填料和高速公路。部分饱和土的力学特性由于三者之间复杂的相互作用而尚未得到很好的理解。该奖项支持基础研究，使用实验和计算机建模方法，提供在各种加载条件下部分饱和土壤经历变形和体积变化（即固结）的机制所需的知识。这项工作有可能改变目前对部分饱和土壤的理解，这与采样、测试、表征和监测以及使用这些材料的可持续民用基础设施的设计和建设有关。本研究项目的目的是对部分饱和土的多阶段固结进行全面的实验和计算研究，然后评估这些研究结果在岩土工程和地球环境工程中的相关应用意义。这项工作具有内在的科学价值，在推进当前对广泛的物理过程的理解方面，以及在开发用于广泛工程应用的沉降，流体流动，有效应力和最终材料特性剖面的改进预测方法方面的实际效用。试验计划将包括对各种变化应力和水文条件下的土壤进行的多相固结试验。实测数据将采用基于统一有效应力理论和吸力应力特征曲线的统一框架进行解释。计算程序将使用新颖的三拉格朗日（固体-水-空气）离散方法开发新模型，以跟踪每个相的运动，同时考虑几何和材料非线性、可压缩非达西气体流动、耦合流动效应、相不连续以及机械和水文滞后。一旦得到验证，新模型将用于进行数值模拟研究，以评估多相土壤固结对各种工程应用的重要性，并强调这些影响对更广泛的岩土工程和地质环境工程界的重要性。

Partially saturated soils are three-phase earth materials that contain both air and water in the void space between the solid grains. Such soils are commonly encountered in field construction for a wide range of civil engineering works, including foundations, landfills, slopes, retaining walls, compacted fills, and highways. The mechanical behavior of partially saturated soils is not well understood because of complex interactions of the three phases. This award supports fundamental research, using both experimental and computer modeling methods, to provide needed knowledge of the mechanisms by which partially saturated soils undergo deformation and volume change (i.e., consolidation) under various loading conditions. This work has the potential to transform current understanding of partially saturated soils, which has relevance to sampling, testing, characterization, and monitoring, as well as design and construction of sustainable civil infrastructures using these materials.The objective of this research program is to conduct a comprehensive experimental and computational investigation of multiphase consolidation for partially saturated soils, and then assess the significance of these findings for relevant applications in geotechnical and geoenvironmental engineering. This work has both intrinsic scientific merit in terms of advancing the current understanding of a widespread physical process, as well as practical utility in terms of developing improved prediction methods for settlement, fluid flow, effective stress, and final material property profiles for a wide range of engineering applications. The experimental program will include multiphase consolidation tests conducted for a variety of soils with changing stress and hydrologic conditions. Measured data will be interpreted using a new and consistent framework based on unified effective stress theory and the suction stress characteristic curve. The computational program will develop new models using a novel tri-lagrangian (solid-water-air) discretization method to track movements of each phase while accounting for geometric and material nonlinearities, compressible non-Darcy gas flow, coupled flow effects, phase discontinuities, and mechanical and hydrologic hysteresis. Once validated, the new models will be used to perform numerical simulation studies to assess the significance of multiphase soil consolidation for a variety of engineering applications and highlight the importance of these effects to the broader geotechnical and geoenvironmental engineering community.