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

部分饱和土壤是固体颗粒之间的空隙中同时含有空气和水的三相土体材料。在各种土木工程的实地施工中，包括地基、堆填区、斜坡、挡土墙、压实填土和公路，这种土是很常见的。由于三相复杂的相互作用，对部分饱和土力学行为的认识还不是很清楚。该奖项支持使用实验和计算机模拟方法的基础研究，以提供所需的关于部分饱和土壤在各种载荷条件下发生变形和体积变化(即固结)的机制的知识。这项工作有可能改变目前对部分饱和土壤的理解，这与取样、测试、表征和监测以及使用这些材料设计和建造可持续的民用基础设施有关。本研究计划的目标是对部分饱和土壤进行全面的多相固结实验和计算调查，然后评估这些发现在岩土工程和岩土环境工程中的相关应用意义。这项工作既具有内在的科学价值，可以促进当前对广泛的物理过程的理解，也可以在为广泛的工程应用开发改进的沉降、流体流动、有效应力和最终材料特性剖面的预测方法方面具有实用价值。该实验计划将包括对各种应力和水文条件变化的土壤进行多相固结试验。测量数据将使用基于统一的有效应力理论和吸应力特征曲线的新的和一致的框架来解释。该计算程序将使用一种新的三拉格朗日(固体-水-空气)离散化方法来开发新的模型，以跟踪每一相的运动，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、相不连续性以及机械和水文滞后。一旦得到验证，新的模型将被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.