Three Dimensional Experiments of Clay with Controlled Microfabric

***9872618 pennmad1 .将采用轴扭和真三轴试验进行局部应变测量的多轴试验，在不排水条件下，评估与主应力方向旋转相关的应力路径中粘土的应力-应变关系。实验还包括评估粘土的初始微结构与其作为施加载荷的函数的演变性质之间的关系。将使用扫描电子显微图（SEM）的数字图像分析和汞侵入孔隙度法对微织物进行定量评估。使用数字扫描电镜和强度梯度分析来评估固体（粘土薄片）的排列。利用织物指数和取向倾角这两个参数对微织物进行定量描述。可重复的空心圆柱体和立方体高岭石粘土样品具有可控和均匀的初始结构，将从两个阶段的浆料固结过程中获得，粘土将在预定的应力水平下进行各向同性和各向异性固结。二维和三维孔隙结构将通过特征孔径分布曲线进行独特描述，并进行分析以评估屈服和破坏标准。在广义三维应力状态下，将评估屈服面和破坏面与微织物、试样形状以及与仪器类型相关的差异的相关性。该研究计划将提供：a)描述粘性土微结构的定量方法；b)更好地理解粘土的力学行为及其与微结构在各种加载条件下的关系；c)为建模界建立考虑微结构效应的粘性土三维本构模型提供数据库

***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.***