The Importance of Osmosis in the Volumetric Behavior of Undisturbed and Expansive Earth Materials

渗透机制作为影响诸如膨胀地面和滑坡等灾害的岩土工程意义尚未明确。主要的障碍是缺乏适当的定量方法来就地预测或测量这些机制的规模。这项研究将是为全面评价自然地质系统中渗透机制对岩土工程问题的重要性建立定量基础的重要一步，例如：2)黄铁矿氧化等风化机制在破坏地面稳定和引发滑坡中的作用；3)低渗透环境中地下水运动和异常孔隙流体压力的地球化学原因；4)污染地面的修复。目前对渗透机制的理解主要是基于对沉积地质盆地中异常地下水压力和组成的有争议的实地研究，以及对具有单电解质孔隙流体的单矿物粘土的实验室和理论研究。天然土材料渗透机制的实验室研究和这些机制在岩土工程系统中的明确的现场研究还处于起步阶段。本研究的目标是：1)建立一种综合的实验和理论方法来量化天然土材料原状样品的渗透机制；2)利用这种方法来量化影响皮埃尔页岩膨胀行为的渗透机制的重要性，即渗透驱动的孔隙流体通量和渗透诱导的粘土颗粒之间的体积排斥。实现这些目标的目标包括：1)利用三轴系统测量孔隙流体组分的耦合通量；2)在Pierre页岩急倾地层中选择、采样和表征一个测试点，使用传统方法和新的实验系统；3)扩展现有的耦合流动理论，从渗透机制中包括膨胀粘土页岩的膨胀压力和体积变化；4)用新的理论框架分析新的实验数据，量化渗透驱动的孔隙流体通量和渗透诱导的粘土颗粒间体积排斥效率的地质、物理和化学控制。

The geotechnical significance of osmotic mechanisms as influencing hazards such as expansive ground and landslides has yet to be clarified. The major obstacle has been the lack of appropriate quantitative methods for either predicting or measuring the magnitudes of these mechanisms in situ. This research will be an essential step towards establishing a quantitative basis for comprehensive evaluation of the significance of osmotic mechanisms for geotechnical problems in natural geologic systems such as: 1) damaging differential displacements in expansive ground, 2) the role of weathering mechanisms, such as oxidation of pyrite, in destabilizing ground and triggering landslides 3) geochemical causes of groundwater movement and abnormal pore-fluid pressures in low-permeability environments, and 4) the remediation of contaminated ground. The current understanding of osmotic mechanisms is based primarily on controversial field studies concerning anomalous groundwater pressures and compositions in sedimentary geologic basins, and also on laboratory and theoretical studies of monominerallic clays with uni-electrolyte pore fluids. Laboratory studies of osmotic mechanisms on natural earth materials and unambiguous field studies of these mechanisms ion geotechnical systems are in their infancy. The goals of this research are: 1) to develop an integrated experimental and theoretical approach for quantifying osmotic mechanisms on undisturbed samples of natural earth materials, and 2) to use this approach to quantify the importance of osmotic mechanisms that influence the expansive behavior of the Pierre Shale, namely osmotically-driven pore fluid flux and osmotically-induced volumetric repulsion among clay particles. The objectives for accomplishing these goals include: 1) mobilizing a triaxial system for measuring the coupled fluxes of pore fluid constituents, 2) selecting, sampling, and characterizing a test site in steeply dipping strata of Pierre shale, using both conventional methods and the new experimental system, 3) expanding existing coupled-flow theory to include swelling pressures and volume changes in expansive clay shales from osmotic mechanisms, and 4) analyzing the new experimental data with the new theoretical framework to quantify the geologic, physical, and chemical controls on the efficiencies of osmotically-driven pore fluid flux and osmotically-induced volumetric repulsion among clay particles.