Three Dimensional Experiments of Clay with Controlled Microfabric

* 9872618 Pennmadu将使用轴向扭转和真三轴试验进行局部应变测量的多轴试验，其中将评估粘土的应力-应变关系，以确定与不排水条件下主应力方向旋转相关的应力路径。 实验还包括评估粘土的初始微组构与其演化性质之间的关系，作为施加载荷的函数。微组构将使用扫描电子显微镜（SEM）的数字图像分析和压汞法进行定量评估。 使用数字SEM和强度梯度分析评估固体（粘土片晶）的排列。 微组构将使用两个参数定量描述：组构指数和取向倾角。可重复的空心圆柱体和立方体高岭石粘土试样与控制和均匀的初始织物将获得从两个阶段的泥浆固结程序，粘土将受到各向同性和各向异性固结预定的应力水平。 二维和三维孔隙结构将由特征孔径分布曲线唯一地描述，并将进行分析以评估屈服和失效准则。屈服和失效表面对微观结构、试样形状以及与设备类型相关的差异的依赖性将在广义三维应力状态下进行评估。 该研究计划将提供：a）描述粘性土微组构的定量程序，B）更好地理解各种荷载条件下粘土的力学行为及其与微组构的关系，以及c）建模社区开发三维本构模型的数据库考虑微组构效应。

***9872618PennmaduMulti-axial experiments with local strain measurements will be performed using axial-torsional and true triaxial testing in which he stress-strain relationship of clays will be evaluated for the stress paths associated with the rotation of principal stress directions under undrained conditions. Experiments also include evaluating the relationship between the initial microfabric of clay and the nature of its evolution as a function of the applied loading.The microfabric will be evaluated quantitatively using digital image analysis of scanning electron micrographs (SEM), and using mercury intrusion porosimetry. The arrangements of solids (clay platelets) is evaluated using digital SEM and the intensity gradient analysis. The microfabric will be described quantitatively using two parameters: fabric index and the inclination of orientation. Repeatable hollow cylinder and cubical kaolinite clay specimens with a controlled and uniform initial fabric will be obtained from a two stage slurry consolidation procedure, and the clays will be subjected to both isotropic and anisotropic consolidation for predetermined stress levels. The two- and three-dimensional void fabric will be uniquely described by a characteristic pore size distribution curve, and analysis will be performed to evaluate yield and failure criteria.The dependency of yield and failure surfaces on the microfabric, specimen shape, and the differences associated with apparatus type will be evaluated under the generalized three-dimensional stress states. The research plan will provide: a) quantitative procedures for describing the microfabric of cohesive soil, b) a better understanding of mechanical behavior of clay and its relationship with microfabric for a wide variety of loading conditions, and c) a database for the modeling community to develop three-dimensional constitutive model for cohesive soil accounting for microfabric effects.***