Liquefaction strength of fly ash reinforced with randomly distributed fibers

In this paper a study on the improvement of liquefaction strength of fly ash by reinforcing with randomly distributed geosynthetic fiber/mesh elements is reported. A series of stress controlled cyclic triaxial tests were carried out on fly ash samples reinforced with randomly distributed fiber and mesh elements. The liquefaction resistance of reinforced fly ash is defined in-terms of pore pressure ratio. The effects of parameters such as fiber content, fiber aspect ratio, confining pressure, cyclic stress ratio, on liquefaction resistance of fly ash have been studied. Test results indicate that the addition of fiber/mesh elements increases the liquefaction strength of fly ash significantly and arrests the initiation of liquefaction even in samples of loose initial condition and consolidated with the low confining pressure.     

单图像三维立体图简介

立体图指的是在观察图画中的深度时，通过双眼的配合能够构造出一幅心理上的立体透视图来。人们常规的做法是使用一对像图来获得立体景色，这样的图要经适当的制作并要用双眼分别各看一张。近年来，借助于计算机产生的随机点图可用来勾绘出实物。这种随机点图如用单只眼睛观看时则是毫无意义的，但如用双眼观看时便可产生出立体景色。原先这样的随机点立体图似乎均要求制成两张图，但最近的工作表明将此种图合二而一的方法已获成功。     

某水电站地下洞室随机块体稳定性评价及系统锚固设计

地下洞室中的随机块体是指由岩体中的随机节理或者基体裂隙构成的不确定性块体 ,在已建的地下厂房中 ,这类块体大量存在 ,这类块体的稳定性会对洞室的施工安全造成较大的影响。在设计中这类块体常常是通过系统锚杆进行加固 ,但由于块体位置随机性和几何特征的不确定性 ,使得系统锚杆的长度和间距很难确定。本文以某水电站的地下洞室为研究对象 ,在深入了解地质条件、岩体结构特点的基础上 ,找出可能构成随机节理的分布规律 ,再分析节理与节理、节理和Ⅰ、Ⅱ类确定性结构面可能的组合 ,得到可能的随机块体 ,然后采用块体理论评价其稳定性 ,得到随机块体的几何特征和稳定状况 ,总结出最优的锚杆长度 ,为地下洞室的系统锚杆长度的确定提供了理论依据     

Reliability analysis of seismic bearing capacity of strip footing by stochastic slip lines method

In this research, the reliability analysis of seismic ultimate bearing capacity of strip footing is assessed with implementing slip lines method coupled with random field theory. The probability density functions of seismic and static bearing capacities which are log-normal and nearly normal distribution respectively are compared to each other. The predicted Probability Density Function (PDF) of the seismic bearing capacity by slip line method is verified, with those of the Terzaghi equation and Monte Carlo simulation (MCs). For uncertainties analysis by Terzaghi equation the N_c, N_q and N_γ are assessed stochastically.     

Three-dimensional slope reliability and risk assessment using auxiliary random finite element method

This paper aims to propose an auxiliary random finite element method (ARFEM) for efficient three-dimensional (3-D) slope reliability analysis and risk assessment considering spatial variability of soil properties. The ARFEM mainly consists of two steps: (1) preliminary analysis using a relatively coarse finite-element model and Subset Simulation, and (2) target analysis using a detailed finite-element model and response conditioning method. The 3-D spatial variability of soil properties is explicitly modeled using the expansion optimal linear estimation approach. A 3-D soil slope example is presented to demonstrate the validity of ARFEM. Finally, a sensitivity study is carried out to explore the effect of horizontal spatial variability. The results indicate that the proposed ARFEM not only provides reasonably accurate estimates of slope failure probability and risk, but also significantly reduces the computational effort at small probability levels. 3-D slope probabilistic analysis (including both 3-D slope stability analysis and 3-D spatial variability modeling) can reflect slope failure mechanism more realistically in terms of the shape, location and length of slip surface. Horizontal spatial variability can significantly influence the failure mode, reliability and risk of 3-D slopes, especially for long slopes with relatively strong horizontal spatial variability. These effects can be properly incorporated into 3-D slope reliability analysis and risk assessment using ARFEM.     

复杂金属矿体地震波正演模拟研究-以庐枞罗河-泥河-大包庄矿床为例

地震勘探在金属矿勘查中发挥越来越重要的作用,但复杂的介质结构和矿体形态通常使金属矿地震解释异常困难,为深入研究复杂金属矿体的地震波场特征,有效开展金属矿地震解释,本文以庐枞矿集区的罗河、泥河和大包庄矿床为例,在详细开展物性测量和地质与地球物理建模的基础上,对均匀介质复杂矿体模型、简化矿体模型和随机介质简化矿体模型进行了...     

Rock-soil slope stability analysis by two-phase random media and finite elements

To investigate the strong random nature of the geometric interfaces between soil and rock, a rock-soil slope is considered as a two-phase random medium. A nonlinear translation of a Gaussian field is utilized to simulate the two-phase random media, such that the soil(or rock) volume fraction and the inclination of the soil layer can be examined. The finite element method with random media incorporated as the material properties is used to determine the factor of safety of the rock-soil slope. Monte-Carlo simulations are used to estimate the statistical characteristics of the factor of safety. The failure mode of the rock-soil slope is examined by observing the maximum principal plastic strain at incipient slope failure. It is found that the critical surface of a rock-soil slope is fairly irregular, and it significantly differs from that of a pure soil slope. The factor of safety is sensitive to the soil volume faction, but it is predictable. The average factor of safety could be well predicted by the weighted harmonic average between the strength of soil and rock; the prediction model is practical and simple. Parametric studies on the inclination of the soil layer demonstrate that the most instable scenario occurs when the slope angle is consistent with the inclination of the soil layer.     

Contribution of ionospheric irregularities to the error of dual-frequency GNSS positioning

This paper investigates the third-order residual range error in the dual-frequency correction of ionospheric effects on satellite navigation. We solve the two-point trajectory problem using the perturbation method to derive second-approximation formulas for the phase path of the wave propagating through an inhomogeneous ionosphere. It is shown that these formulas are consistent with the results derived from applying perturbation theory directly to the eikonal equation. The resulting expression for the phase path is used in calculating the residual range error of dual-frequency global positioning system (GPS) observations, in view of second- and third-order terms. The third-order correction includes not only the quadratic correction of the refractive index but also the correction for ray bending in an inhomogeneous ionosphere. Our calculations took into consideration that the ionosphere has regular large-scale irregularities, as well as smaller-scale random irregularities. Numerical examples show that geomagnetic field effects, which constitute a second-order correction, typically exceed the effects of the quadratic correction and the regular ionospheric inhomogeneity. The contribution from random irregularities can compare with or exceed that made by the second-order correction. Therefore, random ionospheric irregularities can make a significant (sometimes dominant) contribution to the residual range error.