Experiment Study and Interpretation on Relation between Modulus of Rock and Strain Amplitude

INTRODUCTIONThe modulus of rock is one of the basic elastic parameters of the earth’s medium. Under theassumption of linear elastic theory and Poisson medium,other parameters can be calculated fromit .But the real earth mediumis nonlinear elastic and has not a simple linear relationship between stressand strain.This causes relatively big differences betweenthe dynamic andthe static modulus of rock.In nonlinear elastic theory,the Young’s modulusEis replaced bythe nonlinear elastic modul…     

Multi-Layer Strain Rate Field Controlled by Netlike Plastic-Flow in the Lithosphere in Central-Eastern Asia

INTRODUCTIONAccording to the“netlike plastic-flow (NPF)”continental dynamics model ( Wang, 1993a ,1993b; Wang,et al .,2001c) ,the continental lithosphere generally includes 4 tectonic deformationlayers frombottomtotop:the NPFlayer (i .e .thelowerlithosphere ,includingthelithospheric mantleandlower crust) ,the transitional weak layer distributed discontinuously (i .e .the so-called low-velocity/high-conductivitylayer) ,the shear fracturinglayer (i .e .the seismogenic layer inthe upperc…     

On an Earth ellipsoid best-fitted to the Earth surface

Historically, the mean Earth ellipsoid is obtained by fitting an ellipsoid of revolution to the geoid. Such an ellipsoid, however, does not necessarily best fit the physical surface of the Earth due to the existence of topography outside the geoid. In this paper, we present a purely geometrically defined Earth ellipsoid that best fits the physical surface of the Earth so that the resulting ellipsoidal height attains minimum global mean square value. Using a global digital terrain model and a global geopotential model, the size, shape and position of such an Earth ellipsoid have been numerically estimated. Received: 6 September 1996 / Accepted: 1 April 1998     

溶藻细菌MS7的分类鉴定及其溶藻活性的初步研究

采用形态学、生理生化指标和16SrRNA基因序列同源性分析的方法,对菌株MS7进行鉴定,并通过溶藻试验测定该菌株对铜绿微囊藻(Microcystis aeruginosa)的溶藻活性和溶藻方式。结果表明,MS7菌株为苏云金芽孢杆菌(Bacillus thuringiensis),对铜绿微囊藻具有高效溶藻效果,当菌浓度为108cells/mL,初始藻液叶绿素a浓度为0.7mg/L时,48h溶藻率达到91%。主要通过分泌胞外物质的间接方式溶藻,溶藻物质属于具有很强的热稳定性的非蛋白质类物质。     

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Sedimentary stylolite networks and connectivity in limestone: Large-scale field observations and implications for structure evolution

Stylolites are rough surfaces, formed by localized rock dissolution, and prevalent in carbonates and other sedimentary rocks. Their impact on porosity and permeability, and capacity to accommodate compactive strain, are well documented. This paper presents a meso-scale field study on sedimentary stylolites in carbonates, characterizing large-scale distributions of stylolites, including measurements conducted on longer than kilometer-long stylolites. Our field study suggests that on large scales connections between stylolites become important. Since connectivity, and also lack of connectivity, are expected to play a significant role in strain accommodation and hydraulic rock properties, we suggest that large-scale analysis may require a new characterization scheme for “stylolite populations”, based on their connectivity. We therefore divide sedimentary stylolite populations into three end-member types, which are correlated with the three possibilities for percolation of such systems: isolated stylolites (with zero percolation/connectivity), long-parallel stylolites (with 2-dimensional percolation/connectivity), and interconnected stylolite networks (with 3-dimensional percolation/connectivity). New statistical parameters and measures are devised and used to quantitatively characterize the different population types. Schematic mechanistic models are then offered to explain the evolution of the three end-member connectivity-classes. In addition we discuss the effect on fluid flow of the different population types.     

Discrete modeling of strain accumulation in granular soils under low amplitude cyclic loading

An advanced understanding of the strain accumulation phenomenon in granular soils subjected to low amplitude cyclic loading with relatively high frequency is needed to enhance the ability to predict the settlement of granular soils induced by vibrations. In the current study, the discrete element method is used to study this phenomenon. A loose and a medium dense sample composed of a relatively large number of spheres are considered. A series of stress controlled cyclic triaxial tests with different excitation amplitudes and frequencies is performed on these samples at different static stress states. The response of these samples at the macroscopic and microscopic scales is analyzed. The sample density, the cyclic stress amplitude and the static stress state importantly affect strain accumulation. However, the cyclic excitation frequency has a small effect on strain accumulation. At the microscopic scale, frictional sliding occurring at a few contacts continuously dissipates energy and the fraction of these contacts varies periodically during cyclic loading. The coordination number of these samples increases slightly as strain accumulates. However, the anisotropy remains almost constant during low amplitude cyclic excitation. A qualitatively good agreement between numerical and experimental results is found.     

椭球体的视电阻率特征

椭球体是最具代表性的典型三维地电体之一,它三个轴的长短经过变化后可以和多种形状的地电体相似。因此,实现了椭球体电阻率的求解,就可以模拟绝大多数三维地电体的电阻率曲线。从拉普拉斯方程的求解出发,得到了均匀空间中存在的水平椭球体异常表达式,并用简单加倍的方法得到了均匀半空间中水平椭球体的视电阻率公式,结合倾斜旋转椭球体的视电阻率公式的规律,得到了倾斜椭球体的视电阻率公式,再进行一系列简化得到板状体。最后分析对比了均匀电场中旋转椭球体和板状体的视电阻率曲线的形态和规律。结论表明:旋转椭球体与板状体的视电阻率曲线的走向大体相似,且板状体的曲线相比旋转椭球体较缓和。对于低阻情况,在异常体顶部附近的视电阻率异常为零,异常体的倾向一侧有极小值,反倾向一侧有极大值,曲线随倾角α的增大而逐渐变陡。对于高阻情况,视电阻率的极大值出现在异常体顶部附近,两侧有极小值,倾向一侧的曲线较缓和而反倾向一侧的曲线较陡峭,随着倾角α的增大,视电阻率异常变大。     

自定义坐标系的建立及其坐标变换实现

大地基准(含数学椭球体)和投影方式的组合形成多种投影坐标系。地质勘查工作者常遇到坐标转换问题和建立自定义坐标问题,尤其是当我国北京54坐标系和西安80坐标系地质数据的GIS化时。GIS软件已经成为地质勘查的基本工具,而地质数据GIS化的第一步就是建立坐标系统。本文论述了如何使用Map Info和GeosoftOasis MontajTM两种常见地质勘查GIS软件建立自定义坐标,主要是如何在该两个软件中构建自定义大地基准(datum),并且给出了如何使用两个软件进行坐标变换的步骤。     

斜轴变形椭球高斯投影方法

针对东西跨度较大的线路,借助最小二乘法建立斜轴参考椭球,以减小高斯投影横坐标;通过坐标系转换理论,推导出测区在各坐标系下的空间直角坐标,进而确定测区相对于斜轴参考椭球上的大地坐标;利用椭球变换法建立斜轴变形椭球以减小因高程引起的投影变形。以某铁路线为例,可知"斜轴变形椭球高斯投影方法"可大大减小投影后横轴方向分量,避免高斯投影分带现象,同时有效减小高程及其引起的投影变形。该方法数学模型严谨、运算过程清晰,便于编制相关软件,可投入工程使用。