关于堆石料三维流变速率的一点注记

原型监测表明面板堆石坝一般存在比较显著的流变现象。针对不同文献给出的堆石料三维剪切流变速率计算式存在差异,笔者以3参数指数流变模型为例对堆石料三维流变速率进行了研究。假设体积流变和剪切流变变化规律不同,首先推导了三维体积流变速率计算公式,然后依据Prandtl-Reuss流动法则可以由Mises屈服函数作为塑性势函数推导获得。为此,采用关联流动法则,同时假设塑性势函数为Mises屈服函数,导出了堆石料三维剪切流变速率计算式。通过将三维流变速率计算式退化为单轴流变速率计算式进行合理性分析,分析表明,本文导出的三维流变速率计算式理论上是严谨的,由此指出相关文献给出的流变速率计算式理论上不严谨。     

稳态与湍流特征测试对通量数据质量的评价

应用CO2通量、感热和潜热通量稳态测试及垂直速度积分测试相结合的湍流数据质量评价方法对锡林浩特国家气候观象台2009年全年的湍流通量观测数据进行了质量评价。结果表明,锡林浩特通量观测数据质量总体较好;80％以上数据通过质量评价为较好数据;质量评价较好的数据分布呈白天大于夜间、夏季大于冬季的特点。经过对比分析,前期数据处理能剔除大部分质量不好的数据,但应用稳态测试与湍流积分测试筛选后,数据质量仍有明显提高,能量闭合率较前期数据分析前提高2％以上。     

Adaptive state estimation of groundwater contaminant boundary input flux in a 2-dimensional aquifer

In many circumstances involving heat and mass transfer issues,it is considered impractical to measure the input flux and the resulting state distribution in the domain.Therefore,the need to develop techniques to provide solutions for such problems and estimate the inverse mass flux becomes imperative.Adaptive state estimator(ASE)is increasingly becoming a popular inverse estimation technique which resolves inverse problems by incorporating the semi-Markovian concept into a Bayesian estimation technique,thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters.The ASE is particularly designed for a system that encompasses independent unknowns and/or random switching of input and measurement biases.The present study describes the scheme to estimate the groundwater input contaminant flux and its transient distribution in a conjectural two-dimensional aquifer by means of ASE,which in particular is because of its unique ability to efficiently handle the process noise giving an estimation of keeping the relative error range within 10%in 2-dimensional problems.Numerical simulation results show that the proposed estimator presents decent estimation performance for both smoothly and abruptly varying input flux scenarios.Results also show that ASE enjoys a better estimation performance than its competitor,Recursive Least Square Estimator(RLSE)due to its larger error tolerance in greater process noise regimes.ASE's inherent deficiency of being slower than the RLSE,resulting from the complexity of algorithm,was also noticed.The chosen input scenarios are tested to calculate the effect of input area and both estimators show improved results with an increase in input flux area especially as sensors are moved closer to the assumed input location.     

Bulk modulus of Fe-rich olivines corrected for non-hydrostaticity

In situ X-ray diffraction was used to measure the isothermal bulk modulus at room conditions (K_T0) of synthetic olivines with different iron contents. The chemical formulae of the olivine samples were ${({\mathrm{Fe}}_x,{\mathrm{Mg}}_{1?x})}_2\mathrm{Si}{\mathrm{O}}_4$ with x = 0.45; 0.64; 0.82; 1, with 1% standard deviation (referenced as Fa45, Fa64, Fa82 and Fa100, respectively). All experiments were performed in the multi-anvil apparatus installed at NSLS beamline X17B2, to pressures up to about 7 GPa. Unit-cell volumes under hydrostatic conditions and differential stresses present in the samples were calculated using the method developed by Singh et al. (1998), and pressures measured using NaCl as a standard were then corrected for these stresses. Using a second-order Birch–Murnaghan equation of state, we obtained the isothermal bulk modulus of each composition: $K_{T0}^{\mathrm{Fa45}}=131.4\pm 2.6$ GPa, $K_{T0}^{\mathrm{Fa64}}=132.1\pm 3.1$ GPa, $K_{T0}^{\mathrm{Fa82}}=136.3\pm 1.7$ GPa and $K_{T0}^{\mathrm{Fa100}}=134.8\pm 1.4$ GPa. These values combined with data available in the literature show that the K_T0 of Fe-rich olivines increases very slowly with the Fe content, but possibly not in a simple linear trend.     

Performance-based analysis and design for internal stability of MSE walls

ABSTRACT

Mechanically stabilized earth (MSE) walls must be designed with adequate margins of safety against internal stability failure described by tensile strength and pullout limit states. Probabilities of failure (or reliability index) will vary strongly with the accuracy of the underlying models that appear in limit state performance functions. In this paper, prior work by the authors and co-workers on this topic is reviewed. Relative performance is explored in the context of the reliability (or probability of failure) of steel and polymeric reinforcing elements in MSE walls using limit state performance functions with load and resistance models having different accuracy.     

套管井应力集中诱导井周波速各向异性的研究

针对在套管井中应用正交偶极声测井检测地层各向异性和确定异常构造应力的需要, 本文通过求解水平构造应力作用下套管井的应力场分布,应用声弹性理论说明应力集中对套管井井周弹性波速空间分布的影响,分析了波速空间分布对加套管后的正交偶极各向异性声测量的影响.井孔、套管、水泥环和地层系统的复杂性改变了原裸眼井情况地层中的应力场分布,使应力集中的范围明显缩小到井眼附近.对应不同方位径向偏振横波的交叉点向井孔附近移动.横波波速空间分布的方位极值规律发生变化,但纵波波速空间分布的方位极值规律不变,仍能提供最大远场构造应力施加的方向.     

1991～2002年新疆中强震震源机制解分析

系统给出了1991～2002年新疆44次中强震震源机制解结果。分析结果认为：这一时段新疆主要受NNE向水平挤压应力制约,但还存在较为明显的NW向应力分布,此结果与新疆近SN向的背景应力场有一些差异。近期中强震震源断层具有多样性,表明新疆构造运动的复杂性;不同时期主压应力P轴仰角的变化,与新疆地震活动的强弱交替相关,显示出区域应力场的增强和恢复过程。多种分析结果表明,自1995年开始新疆区域应力场状态发生了较明显的变化。     

地震动态触发机制的初步研究

提出地震的动态触发模式。用三维非线性动态有限元方法研究了地震的动态触发的可能机制。模拟结果表明,应力波在反射后发生半波损失,压缩波可以转变成拉伸波,反之亦然。因此,动应力包含有拉伸应力。拉伸波叠加或干涉形成较大的动态应力,减小围压,因此减小了内摩擦力,从而触发地震,研究表明断层形态会影响动态应力,认为地震触 发的位置与孕震体边界形状有关。本文还结合有关地学理论和资料,对以上结果进行了相应的分析并给出物理解释。     

Thermodynamic mixing properties of olivine derived from lattice vibrations

We use a lattice vibrational technique to derive thermophysical and thermochemical properties of fayalite, Fe₂SiO₄. This semi-empirical technique is based on an extension of Kieffer’s model to incorporate details of the phonon spectrum. It includes treatment of intrinsic anharmonicity and electronic effects based on crystal field theory. We extend it to predict thermodynamic mixing properties of olivine (Mg,Fe)₂SiO₄ solid solutions by using results of our previous work on the system MgO–SiO₂. Achieving this requires a relation between phonon frequency and composition and a composition relation for the energy of the static lattice. Directed by experimental Raman spectroscopic data for specific optic modes in magnesium–iron solid solutions of olivine and pyroxene we use an empirical relation for the composition dependence for phonon frequencies. We show that lattice vibrations have a large effect on the excess entropy and that the static lattice contribution and lattice vibrations have a large impact on excess enthalpy and excess Gibbs energy. Our model indicates that compositional effects in electronic and magnetic properties are negligible. The compositional variation the Néel temperature has a large impact on excess heat capacity for temperatures below 100 K.     

CO_2-原油体系混相状态的渗流特性

为认识混相状态的CO2在油藏中的渗流特征,利用高温高压三维模拟装置对CO2-地层原油体系在油藏环境条件下的混相驱替过程进行研究.实验发现:模型产出液量与注入量存在较大差异;采收率、含水和气油比曲线亦表现出CO2在孔隙介质中渗流的复杂特征.由实时监测的含水饱和度分布场图分析认为:CO2与原油混相后,流体粘度降低、渗流阻力减小,这是提高采收率的重要原因之一;同时,CO2/原油相与部分接触水能形成近似于三相混相的状态.实验研究还表明CO2以高密度气体形式进入饱和水、饱和油无法进入的微孔隙,这是注入量和产出量不一致的主要原因.