跨孔条件下椭球模型的视电阻率异常特征     

沙磊  蔡柏林 《煤田地质与勘探》1997,25(2):45-49

在跨孔条件下，利用积分方程法计算了孔区内外不同位置、不同产状的三维椭球体模型视电阻率异常。根据所得的典型数值模拟结果，借助视电阻率异常信息剖面图，对异常进行研究，总结了异常特征及其变化规律，并以此为基础分析和认识了其他模型的异常特征。  相似文献   

基于矩形网格的有限差分走时计算方法   总被引：4，自引：0，他引：4       下载免费PDF全文

李振春  刘玉莲  张建磊  马在田  王华忠 《地震学报》2004,26(6):644-650

对于大多数速度场，地震波沿射线传播的初至波走时，可以用有限差分外推的方法在二维或三维数值网格上计算出来. 在保证精度的条件下，为提高计算效率和适应性，本文推导了基于任意矩形网格和局部平面波前近似的有限差分初至波走时计算方法. 另外，该方法对首波和散射波做了合适的处理，而且不会碰到传统射线法存在的阴影区和焦散区等问题. 简单模型和复杂的Marmousi模型试算的结果表明，该方法精度较高并适用于强纵、横向变速的复杂介质. 基于该方法的Kirchhoff叠前深度偏移, 在主要构造和目的层位置的成像效果上基本达到了波动方程法叠前深度偏移的位置成像效果. 由于未考虑续至波等有效能量，在成像的保幅性上不如波动方程法叠前深度偏移的效果，但其计算效率则明显高于全格林函数法和波动方程法.   相似文献   

塔里木盆地北缘库车盆地白垩系风成砂岩研究--以库车河剖面为例   总被引：2，自引：0，他引：2  

梅冥相于炳松  靳卫广 《地质通报》2004,23(12):1221-1227

库车盆地的早白垩世地层为一套干旱气候条件下的红层沉积，包括洪积扇砾岩、间歇性河流砂砾岩、风成细砂岩和粉砂岩、沙漠湖相紫红色泥岩等类型的沉积，组成一个较为典型的沙漠沉积体系。在库车河剖面，下白垩统红层中发育一些厚层至块状的“高能细砂岩和高能粉砂岩”，多为岩屑长石石英砂岩和长石岩屑石英砂岩。它们以良好的分选性和较高的结构成熟度、较细的粒度、较低的成分成熟度和大型交错层理的发育为特征，显示出较为明显的风成沉积特点。  相似文献   

A comparative study on the illite crystallinity and the clay mineral reflectance spectral index for subdividing the very low-grade metamorphic belt along the Lizhou-Hekou geological section in the Youjiang sedimentary basin, Guangxi, China     

YAN Shouxun Laboratory of Remote Sensing Information Sciences  Institute of Remote Sensing Applications  Chinese Academy of Sciences  Beijing  China 《中国科学D辑(英文版)》2004,47(9)

To examine the application potential of hyperspectral remote sensing techniques in classifying very low-grade metamorphic belts, the composition of clay minerals and the cyrstallinity of illite from mudstones were measured using XRD and VIS-SWIR (400-2500 nm) reflectance spectroscopy. Based on the illite cyrstallinity, Kubler Index (KI), the Early Triassic LuoLou Group and the Middle Triassic lower Baifeng Formation were classified as the lower Epizone with KI△2θ° ranging from 0.22 to 0.25, the upper Baifeng Formation as upper anchizone with KI△2θ°ranging from 0.26 to 0.33, and the Hekou Formation as lower anchizone with KI△2θ° ranging from 0.38 to 0.40. According to a KI△2θ° value of 0.43, it is possible that there may exist a local diagenetic zone in the upper strata. The illite cyrstallinity Kubler index and the metamorphic grade increase from the bottom to the top of the stratigraphic sequence. The metamorphic grade boundaries nearly match the stratigraphic boundaries, indicating a burial metamorphism nature for the stratigraphic sequence. From the bottom to the top of the sequence, the spectral absorption band center of clay minerals from fresh rocks is around 2200 nm. The absorption band centers change towards shorter wavelengths: the Luolou Group being at 2220 nm, the Baifeng Formation at 2217-2213 nm, the lower member of the Hekou Formation at 2214-2206 nm, and the upper member of the Hekou Formation at 2205-2197 nm. The spectral absorption band center of illite shows the same change pattern. These results indicate that very low-grade metamorphic belts can be subdivided using spectral indices of clay minerals, which are measured by using field portable spectroradiometers. However, it may not work well with satellite and airborne sensors.  相似文献   

东海PN断面透明胞外聚合颗粒物分布特征及来源研究     

舒逸  张桂成  孙军 《海洋学报》2018,40(8):110-119

透明胞外聚合颗粒物（TEP）是凝聚网的重要组成部分甚至核心，在微尺度范围上形成了水环境结构的重要梯度，对于元素地球化学生物循环、碳沉降以及食物网有着举足轻重的作用。本文研究了东海典型断面PN透明胞外聚合颗粒物的分布特征及来源。结果表明:东海典型断面PN透明胞外聚合颗粒物含量介于28~376 μg Xeq./L之间，平均值为（115±67）μg Xeq./L；呈现出明显的夏季 > 冬季 > 秋季 > 春季的季节变化特征以及近岸 > 外海和底层 > 表层的分布趋势。通过对比透明胞外聚合颗粒物分布趋势和硅藻、甲藻分布趋势以及统计分析得出，东海典型断面PN透明胞外聚合颗粒物主要来源于硅藻，甲藻贡献不大；而外海TEP的来源可能主要由超微型浮游植物贡献。  相似文献   

Dynamic response of a pile considering the interaction of pile variable cross section with the surrounding layered soil          下载免费PDF全文

Liu Gao  Kuihua Wang  Si Xiao  Wenbing Wu 《国际地质力学数值与分析法杂志》2017,41(9):1196-1214

Assuming that the pile variable cross section interacts with the surrounding soil in the same way as the pile toe does with the bearing stratus, the interaction of pile variable cross section with the surrounding soil is represented by a Voigt model, which consists of a spring and a damper connected in parallel, and the spring constant and damper coefficient are derived. Thus, a more rigid pile–soil interaction model is proposed. The surrounding soil layers are modeled as axisymmetric continuum in which its vertical displacements are taken into account and the pile is assumed to be a Rayleigh–Love rod with material damping. Allowing for soil properties and pile defects, the pile–soil system is divided into several layers. By means of Laplace transform, the governing equations of soil layers are solved in frequency domain, and a new relationship linking the impedance functions at the variable‐section interface between the adjacent pile segments is derived using a Heaviside step function, which is called amended impedance function transfer method. On this basis, the impedance function at pile top is derived by amended impedance function transfer method proposed in this paper. Then, the velocity response at pile top can be obtained by means of inverse Fourier transform and convolution theorem. The effects of pile–soil system parameters are studied, and some conclusions are proposed. Then, an engineering example is given to confirm the rationality of the solution proposed in this paper. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Measurement of stream cross section using ground penetration radar with Hilbert–Huang transform          下载免费PDF全文

Yen‐Chang Chen  Su‐Pai Kao  Jhong‐Hua Wu 《水文研究》2014,28(4):2468-2477

This study presents a new method to measure stream cross section without having contact with water. Compared with conventional measurement methods which apply instruments such as sounding weight, ground penetration radar (GPR), used in this study, is a non‐contact measurement method. This non‐contact measurement method can reduce the risk to hydrologists when they are conducting measurements, particularly in high flow period. However, the original signals obtained by using GPR are very complex, different from studies in the past where the measured data were mostly interpreted by experts with special skill or knowledge of GPR so that the results obtained were less objective. This study employs Hilbert–Huang transform (HHT) to process GPR signals which are difficult to interpret by hydrologists. HHT is a newly developed signal processing method that can not only process the nonlinear and non‐stationary complex signals, but also maintain the physical significance of the signal itself. Using GPR with HHT, this study establishes a non‐contact stream cross‐section measurement method with the ability to measure stream cross‐sectional areas precisely and quickly. Also, in comparison with the conventional method, no significant difference in results is found to exist between the two methods, but the new method can considerably reduce risk, measurement time, and manpower. It is proven that the non‐contact method combining GPR with HHT is applicable to quickly and accurately measure stream cross section. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Analysis of rectangular piles subjected to lateral loads in nonhomogeneous soil using a Winkler model approach          下载免费PDF全文

Hiroyoshi Hirai 《国际地质力学数值与分析法杂志》2015,39(9):937-968

An analytical approach using a Winkler model based on two lateral soil displacement components in a three‐dimensional soil is investigated to provide analytical solutions of horizontal response of a rectangular pile subjected to lateral loads in nonhomogeneous soil. The two lateral displacement components of a soil surrounding the rectangular pile are represented by the Fourier series of displacement potential functions in the elastic three‐dimensional analysis. The lateral stiffness coefficient of the rectangular pile shaft in nonhomogeneous soil is derived from the rocking stiffness coefficient taking into account rocking rotation of a rigid pile shaft. The relationship between horizontal displacement, rotation, moment, and shear force for the rectangular pile subjected to horizontal loads in nonhomogeneous soil is obtainable in the form of the recurrence equation. The formulation of lateral displacement and rotation for a rectangular pile subjected to lateral loads on the pile base in nonhomogeneous soil is proposed by taking into account Mindlin's equation and the equivalent thickness for soil layers in the equivalent elastic method. The difference of lateral behavior between square and circular piles subjected to lateral loads is insignificant. The effect of aspect ratio of the rectangular pile on the lateral behavior is great for the lower stiffness ratio between pile and soil and the larger length–equivalent diameter ratio. The effect of the value of Poisson's ratio of soil on lateral stiffness coefficient is relatively small except Poisson's ratio close to 0.5. The comparison of the results calculated by the current method for a rectangular pile subjected to lateral loads in nonhomogeneous soil has shown good agreement with those obtained from the analytical methods and the finite element method. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Geochemical and isotopic characterization of trace fossil infillings: New insights on tracemaker activity after the K/Pg impact event     

《Cretaceous Research》2016

Geochemical and isotopic analyses of the Cretaceous–Paleogene (K/Pg) boundary deposits were conducted at the Caravaca section (External Subbetic, southeast of Spain) in order to evaluate the recovery of the macrobenthic tracemaker community and the bioturbational disturbance. Samples from the infilling material of several lower Danian dark-colored trace fossils (Chondrites, Planolites, Thalassinoides and Zoophycos) located in the uppermost 8-cm of the light upper Maastrichtian strata, as well as samples from the host sedimentary rock of these trace fossils, were analyzed and compared with data from the lower Danian deposits. The values of element ratios indicative of extraterrestrial contamination (Cr/Al, Co/Al and Ni/Al) are higher in the infilling trace fossil material than in the upper Maastrichtian and lower Danian deposits, which suggests a contribution of the ejecta layer. Regarding the isotope composition, the δ¹³C values are lower in the infilling material than in the Maastrichtian host sedimentary rocks surrounding the traces, while the δ¹⁸O are higher in the infilling material. The geochemical and isotopic compositions of the infilling material evidence the unconsolidated character of the sediment, including the red boundary layer. Softground conditions confirm a relatively rapid recovery by the macrobenthic tracemaker community, starting a few millimeters above the K/Pg boundary layer. The mixture of the infilling material of the trace fossils moreover reveals a significant macrobenthic tracemaker activity affecting K–Pg boundary transition sediments that may have significantly altered original signatures.  相似文献   

断面成果数据输出软件的开发及实现     

吴锦发 《测绘工程》2016,25(2):77-80

断面测量的成果一般采用CASS软件绘制成图,但无法输出不同格式的数据文件。以武夷新区崇阳溪保护性开发河道断面测量数据成果为例,对断面数据进行分析,进行技术方法研究,在AutoCAD平台上综合运用Visual LISP和Visual BASIC进行软件开发,编程解决断面成果不同数据格式的输出问题。软件简单实用,并具有批处理功能,具有较好的推广使用价值。  相似文献