硅粉水泥石小角度X射线散射实验研究(Ⅰ)——微孔各向异性

根据X射线小角度散射 (SAXS)理论 ,对描述硅粉水泥石中微孔各向异性程度的特征参数———孔形状因子进行了实验研究 .研究表明 ,所测定的硅粉水泥石中 ,微孔的形状大多数与球形较为接近 ;硅粉含量、水灰比对孔形状因子有较大影响 ;孔形状因子与水泥石强度之间存在着较显著的相关性 .     

硅粉水泥石小角度X射线散射实验研究（Ⅱ）——微孔界面过渡层厚度

采用X射线小角散射(SAXS)技术,测定了硅粉水泥石中微孔孔界面电子密度过渡层厚度,并对过渡层厚度产生的原因进行了探讨.研究表明硅粉水泥石中微孔界面不具有分明的边界,而具有约2×10-9m厚度的电子密度缓变的过渡层;当水灰比较大时,水灰比和硅粉含量对过渡层厚度有较大的影响;水泥石的抗压强度与过渡层厚度存在较显著的相关性.     

硅粉水泥石中微孔孔径分布及其对强度的影响

采用X射线小角度散射(SAXS)技术，对硅粉水泥石中微孔孔径分布(孔半径小于50nm)进行了实验研究，并讨论了孔径分布对强度的影响．研究表明：所测硅粉水泥石的孔径均呈多峰分布，其平均孔半径约在4．5～9．0nm，最可几孔半径约在4．0～6．5nm；硅粉含量、水灰比对孔径分布有显著影响，随着硅粉含量的增加以及水灰比的减小，孔径分布向小孔方向移动；孔径分布与抗压强度有较好的相关性，而孔径分布(孔半径小于50nm)与抗折强度之间不存在明显的相关性．     

硅灰水泥浆体中微孔表面分维及对浆体的影响

采用Ｘ射线小角散射技术对硅灰水泥石中微孔孔表面的分形结构进行了实验研究，并测定其分形维数，同时分析探讨了孔表面分维对孔比表面积、硬化水泥浆体强度等的影响．研究表明，水泥石中微孔孔壁是相当粗糙的，并且均具有分形结构的特点，表面分维与３较为接近；水泥浆体的抗弯、抗压强度以及孔内比表面积等均与微孔表面的分形维数存在一定的联系．     

Anisotropy of turbulence in wind turbine wakes

This work is mainly dedicated to the study of non-isotropic characteristics of turbulence in wind turbine wakes, specifically the shear layer of the near wake. A calculation method based on an explicit algebraic model for the components of the turbulent stress tensor is proposed, and the results are found to be in acceptable agreement with experimental results. Analytical expressions for the estimation of an upper limit of the global turbulence kinetic energy, k, and the individual contributions of each diagonal term in the turbulent stress tensor are proposed. Their predictions are compared with experimental results.     

Anisotropy effect on strengths of metamorphic rocks

This paper aims to study the effect of anisotropy on strengths of several metamorphic rocks of southern(Cine) submassif of Menderes metamorphic massif in southwest Turkey. Four different metamorphic rocks including foliated phyllite, schist, gneiss and marble(calcschist) were selected and examined.Discontinuity surveys were made along lines for each rock and evaluated with DIPS program. L-type Schmidt hammer was applied in the directions parallel and perpendicular to foliation during the field study. Several hand samples and rock blocks were collected during the field study for measurements of dry and saturated densities, dry and saturated unit weights and porosity, and for petrographic analysis and strength determination in laboratory. L-and N-type Schmidt hammers were applied in the directions perpendicular(anisotropy angle of 0°) and parallel(anisotropy angle of 90) to the foliation on selected blocks of phyllite, schist, gneiss and marble(calcschist). The phyllite and schist have higher porosity and lower density values than the other rocks. However, coarse crystalline gneiss and marble(calcschist) have higher rebound values and strengths, and they are classified as strong-very strong rocks. Generally, the rebound values in the direction perpendicular to the foliation are slightly higher than that in the direction parallel to foliation. Rebound values of N-type Schmidt hammer are higher than the L-type values except for phyllite. Sometimes, the rebound values of laboratory and field applications gave different results. This may result from variable local conditions such as minerals differentiation,discontinuities, water content, weathering degree and thickness of foliated structure.     

土体的各向异性及近似模拟

通过真三轴仪试验 ,分别从 3个主应力方向加荷 ,研究产生的应变分量变化 ,从而较清楚地揭示了土体中显著的由应力引起的各向异性。在此基础上提出了土体应力应变柔度矩阵所具有的性质 ,即不同应力方向上加荷所引起的应变分量之间关系的规律 ,这些规律是检验土体本构模型合理性和适用性的重要标尺。依据这些性质 ,提出了一种以邓肯模型为基础修正的各向异性本构模型 ,对于不同的应力方向 ,采用不同的弹性模量和泊松比 ,模型参数与邓肯模型一致 ,由常规三轴试验确定 ,它是一个经验的、但实用性强的各向异性本构模型。     

Anisotropy of strength and deformability of fractured rocks

Anisotropy of the strength and deformation behaviors of fractured rock masses is a crucial issue for design and stability assessments of rock engineering structures, due mainly to the non-uniform and non- regular geometries of the fracture systems. However, no adequate efforts have been made to study this issue due to the current practical impossibility of laboratory tests with samples of large volumes con- taining many fractures, and the difficulty for controlling reliable initial and boundary conditions for large-scale in situ tests. Therefore, a reliable numerical predicting approach for evaluating anisotropy of fractured rock masses is needed. The objective of this study is to systematically investigate anisotropy of strength and deformability of fractured rocks, which has not been conducted in the past, using a nu- merical modeling method. A series of realistic two-dimensional （2D） discrete fracture network （DFN） models were established based on site investigation data, which were then loaded in different directions, using the code UDEC of discrete element method （DEM）, with changing confining pressures. Numerical results show that strength envelopes and elastic deformability parameters of tested numerical models are significantly anisotropic, and vary with changing axial loading and confining pressures. The results indicate that for design and safety assessments of rock engineering projects, the directional variations of strength and deformability of the fractured rock mass concerned must be treated properly with respect to the directions of in situ stresses. Traditional practice for simply positioning axial orientation of tunnels in association with principal stress directions only may not be adequate for safety requirements. Outstanding issues of the present study and su~zestions for future study are also oresented.     

压实黄土强度及渗透各向异性研究

为揭示各向异性对黄土强度和水分场的影响,通过抗剪强度试验和渗透试验对压实黄土强度和渗透各向异性进行研究。结果表明:压实黄土存在强度各向异性,其垂直方向强度参数大于水平方向;压实黄土粘聚力各向异性随含水率增大而减小,干密度对压实黄土粘聚力各向异性无显著影响;含水率和干密度对压实黄土内摩擦角各向异性均无显著影响;压实黄土存在渗透各向异性,水平方向渗透系数大于垂直方向;压实黄土渗透系数随着干密度、围压的增大而减小,且增大到一定程度后变化趋于平缓;干密度、围压对压实黄土渗透各向异性都有较大影响,随着干密度和围压的增大,压实黄土的渗透各向异性会逐渐削弱。     

场地微动各向异性分析及其应用

目前 ,场地微动的理论研究和工程应用均基于各向同性介质模型 ,这与实际情况不符。本文首次提出了场地微动各向异性的概念 ,并从弹性波理论出发 ,对各向异性场地微动进行了研究 ,分析了场地微动各向异性的机制 ,得出了一些有益结论。这对于深入研究各向异性场地条件下场地动力特性、预测地震动力特性、结构抗震研究具有非常重要的意义     

Inverse Analysis of Soft Grounds Considering Nonlinearity and Anisotropy

The inverse analysis method, used to accurately predict the two-dimensional deformation behavior of soft grounds, is discussed in this study. To ensure safety when constructing on a soft ground, in-situ observations are usually made. An inverse analysis is then effective for identifying the in-situ parameters of the ground and for predicting future deformation based on the parameters. The settlement, the lateral displacement, and the pore water pressure are measured during the construction of the structure. It is generally difficult to predict the lateral displacement. In this research, therefore, the cross anisotropy (transverse isotropy) of the ground is introduced to overcome the difficulty of predicting the lateral displacement. Furthermore, a simplified hyperbolic model is introduced to simulate the nonlinear shear behavior. The model is convenient for use with the inverse analysis, since it does not require many parameters. The measured pore water pressure is seldom used in the inverse analysis, because information on the pore water pressure is not required, from a mathematical standpoint, in order to identify the consolidation parameters. The effectiveness of applying the measured pore water pressure for the prediction of future consolidation behavior, is clarified in this study. As a result, the hyperbolic nonlinear model and the assumed anisotropy were found to be useful in predicting the future deformation behavior of clay. Furthermore, the pore water pressure measurement was proved to be effective for the predictions in this study.     

Anisotropy of multi-layered structure with sliding and bonded interlayer conditions

A better understanding of the mechanical behavior of the multi-layered structure under external loading is the most important item for the structural design and the risk assessment. The objective of this study are to propose and develop an analytical solution for the mechanical behaviors of multi-layered structure generated by axisymmetric loading, and to investigate the impact of anisotropic layers and interlayer conditions on the multi-layered structure. To reach these objectives, first, according to the governing equations, the analytical solution for a single layer was formulated by adopting the spatial Hankel transform. Then the global matrix technique is applied to achieve the analytical solution of multi-layered structure in Hankel domain. The sliding and bonded interlayer conditions were considered in this process. Finally, the numerical inversion of integral transform was used to solve the components of displacement and stress in real domain. Gauss-Legendre quadrature is a key scheme in the numerical inversion process. Moreover, following by the verification of the proposed analytical solution, one typical three-layered flexible pavement was applied as the computing carrier of numerical analysis for the multi-layered structure. The results have shown that the anisotropic layers and the interlayer conditions significantly affect the mechanical behaviors of the proposed structure.