高边坡锚,网,喷永久支护防震设计与施工

介绍某边坡工程采用锚、网、喷联合支护取代重力式挡土墙护坡，取得良好技术、经济效益的经验。     

对近年大震震害现象与工程地震问题研究的思考

近年来的几次大地震给人们瘤上了一些值得进一步思考的地震现象，这些现象给工程地震问题研究的发展以启示，也为工程地震问题研究的发展提供了条件，文中粗略地分析了这些地震现象所揭示的工程地震问题，对工程地震中一些问题的研究与发展提出了看法，这些问题包括近源地震动的估计、场地效应及断层效应、地震地面永久变形、地震动衰减关系、地震影响场等。     

G856-ZD质子旋进磁分量仪及其应用

G856-ZD质子旋进磁分量仪是在原G856质子旋进磁力仪的基础上再开发而成的.该仪器采用双CPU工作方式,并且保留了G856质子旋进磁力仪的原有功能.其基本原理是用补偿法测量磁分量.将探头放在一组正交Helmholtz线圈内,同时加上补偿电流,使探头所在的空间得到均匀的补偿磁场,从而实现了磁分量和磁偏角的连续自动观测.     

Changes in the early part of the seismic coda due to localized scatterers: The estimation ofQ in a stope environment

A single scattering model was used to analyse the temporary changes in the mean density of scattered waves in a discrete random medium. The model of the mean energy density, originally proposed bySato (1977) for spherical radiation and isotropic scattering, has been modified and applied to a medium in which the scatterers are confined to a specified volume. The time variation of the early part of the mean energy density function for the different source durations was investigated. The dominant effect on the theoretical mean energy density is caused by the specified volume containing scatterers. The duration of the source pulse influences the early part of the coda fort/t ₀<1.2, wheret is the lapse time measured from the source origin time, andt ₀is arrival time of the body wave.The analysis of the coda signal of micro-events occurring immediately in front of the face enables us to estimate the size of the fracture zone induced by the stope. The model of the mean energy density of coda for a medium containing scatterers close to the seismic source was used to analyse a large number of events recorded close to an advancing mine face in a deep level gold mine in South Africa. The coda decay rate has two trends: the first, with a steep decay of coda, is produced by a larger deviation of rock parameters and/or larger size of the scatterers; the second trend, which decays more slowly, has the corresponding mean-free path ranging from 20 m to 200 m. The analysis indicates that the rock mass about 15–20 m from the stope contains a large proportion of fractured and blocked rock, which is the source of scattering. The scattering of theS-wave was much stronger and more stable, with the mean-free path varying from 11 m to 45 m. This is due to the shorter wavelength of theS wave in comparison with theP wave. The quality factor for theP coda wave varies from 30 to 100 in the fracture zone of stope and outside this zone it has a value of 300. The quality factor of theS wave varies from 20 to 78 in the equivalent volume. For rock surrounding the stope the ratioQ _sp ^–1 /Q _ss ^–1 varied from 0.31 to 0.69. This suggests that the radii of scatterers are smaller than 3.5 m.     

Interpretation,reliability and accuracies of parameters deduced by the spaced antenna method in middle atmosphere applications

The spaced antenna method has proved to be an important and relatively inexpensive radar technique for making measurements of atmospheric wind velocities and other parameters. This discussion examines the reliability and accuracies of various parameters which can be measured with the technique.After a brief introduction, a series of comparisons of winds measured by the spaced antenna method and simultaneously by other techniques are presented. It is concluded that when using weak partial reflections in the height range 0–100km, the spaced antenna technique provides reliable estimates of the neutral air motion. Following this the assumptions made in applying the method are considered in more detail. The possibility of systematic errors and the likelihood of erroneous measurements are examined, and the accuracy of any particular measurement of wind speed is discussed. Previous objections to the technique are discussed, and in general shown to be invalid.Other parameters apart from wind speeds can be measured with the spaced antenna technique, such as pattern scale, the rate of natural fading, and angles of arrival. The meanings of these parameters are discussed in terms of physical quantities such as turbulent energy dissipation rates, small-scale gravity wave velocity fluctuations, and aspect sensitivities of scatterers, and it is indicated when and how these derived parameters can be applied to deduce meaningful physical quantities. The need for great caution in making these interpretations is discussed; for example it is not always possible to use the rate of natural fading to estimate the intensity of turbulence, although in some cases this is possible. Finally, interferometric applications of spaced antenna systems are discussed.     

InSAR中大气改正方法的对比研究

描述了InSAR中大气改正的几种主要方法,对各种方法的优缺点进行了深入的分析,并讨论了各种方法的使用条件和使用中应该注意的问题。改正方法的选择取决于数据条件、研究区域状况、精度要求,也可以多种方法结合使用。最后展望了InSAR中大气改正技术的发展趋势。     

针对超高压输电导线的散射亮斑时间序列分析

针对超高压输电导线在高分辨率雷达影像上表现出的强散射特性,该文提出了一种自动提取输电导线强散射亮斑中心位置的算法。采用自适应窗口最大相关系数法,较精确地提取了强散射斑的位置,实现对散射亮斑亮度、面积、位置的时序分析。基于此算法的实验结果表明:输电导线散射亮斑的亮度峰值、50db以上的散射面积以及中心位置在时序影像中均发生不同程度的变化,并表明散射亮斑位置受导线弧垂影响,且温度是改变弧垂曲率和导线散射几何关系的主要因素。     

LAMBDA方差协方差矩阵迭代估计方法研究

相位解缠是PSDIn SAR技术的一个关键环节,直接关系到地表形变反演的成败。分析了现有LAMBDA相位解缠算法中,观测值方差协方差矩阵确定方法的缺陷;提出了基于先验假设的方差协方差矩阵估计方法;利用上海地区1992—2002年的23幅ERS1/2 C波段卫星数据进行了相位解缠实验,反演的线性形变速率与实际统计数据仅相差1.271 7 mm/a。这表明提出的算法可靠、精度高。     

临时支护与永久支护相结合设计在某工程中的应用

结合具体工程实例,设计了双排桩、土钉墙、桩锚支护、桩顶小挡墙多种支护结构的组合体系,解决了有限空间内临时与永久两种工况下的边坡支护问题。监测结果表明,支护结构位移控制较好,碎石土地层中预应力锚索短期内预应力损失较小。     

Soil slopes under combined horizontal and vertical seismic accelerations

Conventional methods of designing earth structures are based on pseudo-static stability analysis employing a horizontal seismic coefficient. This paper discusses the stability and permanent displacement of a slope subject to combined horizontal and vertical accelerations. A log-spiral failure mechanism is used. It is shown that seismic force has a significant effect on stability and permanent displacement of slopes. The parametric study reveals that vertical acceleration may play an important role on stability and permanent displacement if the corresponding horizontal acceleration is large. © 1997 John Wiley & Sons Ltd.