河岸带蜿蜒性与植被密度对潜流驻留时间的复合效应

潜流驻留时间是反映潜流交换、溶质迁移转化、生物组成、生态过程的重要特征变量。应用双循环可控式河岸带模型，以NaCl为示踪剂，深入研究了河岸带蜿蜒性与植被密度对潜流驻留时间的复合效应；应用量纲分析和主成分分析法，探析了潜流驻留时间的关键影响因子及其作用程度和敏感性。结果表明：①河岸带植被密度对潜流驻留时间具有促进作用，但存在一定的阈值。②潜流驻留时间分布与河岸蜿蜒形态呈类镜像效应；潜流驻留时间在河岸带蜿蜒波不同位置差异明显，迎水面平均驻留时间约为背水面的1/2。③河岸带蜿蜒性与植被密度是影响潜流驻留时间的关键因子，总作用程度达91.07%。潜流驻留时间对蜿蜒性最敏感，对植被密度敏感性较弱，对复合因子的敏感性介于两者之间；迎水面内组合因子对潜流驻留时间具有共同促进效应，背水面内组合因子对潜流驻留时间具有抑制和促进双重效应。     

Fractographic determination of joint length distribution in chalk

Summary Measurements of fracture joint distribution combined with determinations of plume length and orientation on a vertical section of a single chalk layer near Beer Sheva, Israel, reveal that joints marked by unilateral and circular plumes are skewed towards the shorter sizes while joints decorated by bilateral plumes are skewed towards the longer sizes. The mean lengths of the unilateral and bilateral joints are 66.5 cm and 155.6 cm, with standard deviations of 30 cm and 60.6 cm, respectively. These results as well as joint length observations from other areas seem to suggest a bimodal length distribution. However, since the minor maximum is generally very weak, and due to some additional uncertainties, further confirmation of the present observations is needed.     

Estimating the crush zone size under a cutting tool in coal

Summary As part of an effort to understand the mechanics of fine fragment formation in coal, which is important in studies of respirable dust due to mining, fracture toughness measurements and the strain energy density (SED) theory were applied to calculate the crush zone size under a cutting tool in coal. This zone is the major source of fine fragments in the 1 to 10 µm size range. The model used in these calculations is a boundary element program containing a failure criterion based on the SED theory. The boundary element program calculates linear elastic stresses at numerous points in the coal material ahead of a cutting bit. These stresses are then input to a subroutine called critical flaw length and orientation (CFLO) which uses the SED theory to determine the CFLO for a small crack at the boundary element stress computation point. The extent of crushing is based on earlier postulates about the role of inherent flaws in a fragmentation process. To form 1 to 10 µm fragments requires firstly a local stress strong enough to activate flaws with a characteristic length less than 1 to 10 µm and secondly, a flaw density sufficient to provide an average spacing between flaws also on the order of 1 to 10 µm. The locus of active 10 µm flaws represents the maximum possible extent of fine fragmentation in the 10 µm or less size range assuming that a sufficient inherent flaw density exists. The approach offers a first order approximation to the extent of crushing under a tool tip. The size and shape of the crush zone volume is affected by the attack angle and geometry of the tool.     

Shear resistance of jointed rock masses and stability calculation of rock slopes

Summary Based on an extension to a model originally proposed by Zhang (1990), a method for estimating the shear strength of a jointed rock mass containing two joint sets is developed. Compared to the original method in which only a single en-echelon joint set was considered, the new method has the following advantages: (1) it allows a much more realistic joint pattern to be incorporated; (2) the effects of joint connectivity and intersection angle between joint sets on shear strength are included. Use of the new method is demonstrated by application to the calculation of the stability of slopes in jointed rock. The importance of joint connectivity, joint persistence and joint set intersection angle on slope stability, as predicted by the model, is revealed.     

The Fourier Integral Method: An efficient spectral method for simulation of random fields

The Fourier Integral Method (FIM) of spectral simulation, adapted to generate realizations of a random function in one, two, or three dimensions, is shown to be an efficient technique of non-conditional geostatistical simulation. The main contribution is the use of the fast Fourier transform for both numerical calculus of the density spectral function and as generator of random finite multidimensional sequences with imposed covariance. Results obtained with the FIM are compared with those obtained by other classic methods: Shinozuka and Jan Method in 1D and Turning Bands Method in 2D and 3D, the points for and against different methodologies are discussed. Moreover, with the FIM the simulation of nested structures, one of which can be a nugget effect and the simulation of both zonal and geometric anisotropy is straightforward. All steps taken to implement the FIM methodology are discussed.     

中国水质站网规划中几个问题的探讨

在完成中国水质站网规划工作的基础上,对下列问题作了进一步探讨:(1)水质站网规划单元的划分;(2)聚类分析在水质站网规划中的应用;(3)站网密度与人口和经济发展的关系;(4)中国水质站网的分区特征。     

双密度重叠找气新方法

本文根据岩石孔隙中的天然气引起介电测井孔隙度减小和密度测井孔隙度增大的原理,建立了双密度重叠找气新方法,消除了岩性的影响,提高了测井找气的分辨率,增加了评价气层的直观性。该方法用于寻找陕甘宁盆地低孔隙白云岩气藏,获得了明显的地质效果。这种方法还可以在其它储层岩性气藏中应用。