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Wu Li Zhang Shizhong Chen Jianping Faculty of Engineering China University of Geosciences Wuhan 《中国地质大学学报(英文版)》1998,9(3)
INTRODUCTIONTunnelexcavationbyblastingmethodinhardrockisusualyaccomplishedwithadrilandblastprocedurewhereaboreholeisdriledint... 相似文献
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利用MODIS和AMSR-E进行积雪制图的比较分析 总被引:19,自引:2,他引:19
MODIS和被动微波辐射计AMSR-E提供了识别积雪的不同方法.MODIS首先计算反映积雪在1.6μm强吸收特性的归一化差值积雪指数NDSI,在剔除卷云的影响后,得到MODIS积雪分布.AMSR-E则根据积雪在微波波段的差异性散射特性识别积雪.通过案例分析比较了MODIS和AMSR-E积雪分布,发现由于云的遮蔽使MODIS积雪分布面积会比实际小,但由于MODIS的空间分辨率很高,得到的积雪边界线轮廓清晰.而微波由于不受云的影响,得到的AMSR-E积雪分布比较符合实际,但积雪的边界线较粗. 相似文献
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Calculations of the critical dimensionless bed stresses that obtain when upper-stage plane beds should revert to ripple and dune bed forms are presented. Strong support is given to the Bagnold ‘universal’ plane-bed instability criterion and to a modified criterion suggested by Allen over a wide range of solids grain size. A reinterpretation of the mechanism of plane bed instability is based upon the extent to which significant grain concentrations in plane bed flows increase apparent fluid viscosity and decrease turbulence production over potential bed defects, thereby preventing ripple or dune propagation and growth. 相似文献
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We have analyzed the distribution of young objects (open clusters, classical Cepheids, and HII regions) projected onto the plane of the Galaxy using wavelet smoothing. This smoothing technique enables investigation of the large-scale structure of the distribution of young objects. All the studied objects display a similar spiral structure, whose appearance essentially corresponds to a regular alternation of young and older stellar complexes along sections of the spiral arms. A four-arm spiral structure with its arms originating at the Galactic center is obtained if the major arms are taken to be the Carina-Sagittarius arm and an outer arm behind the Perseus arm. If all the observed arms are taken to be major arms, we obtain a 12-arm structure, in contradiction with the size of the region in which the structure is observed in the Galaxy. This discrepancy can be removed if the arms originate from a ring formed by a sufficiently long bar-like structure, rather then from the Galactic center. 相似文献
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地裂缝的成因可以分为天然构造地裂、人为诱发地裂和复合成因地裂、地震断裂,抽水不均匀地面沉降伴生地裂和渗透变形地裂是最主要的地裂缝类型。地裂缝以构造地裂和构造地裂基础上由人为活动诱发现象为主,用优势面观点和方法分析和研究是可行的。根据优势面的原理,提出防灾和减灾的思路,指出地裂灾害预测和预警系统研究对分析、评估和减灾是最有效的手段。防治地裂缝的原则是针对性治理和顺应自然取代对抗,对策是注重避让与选址、引调地表水、做好结构设计和地基处理、制定相应的防灾区域管理法规。 相似文献
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A method is presented for the determination of a triaxial ellipsoid (such as a strain ellipsoid)from three nonparallel plane sections of the ellipsoid. The sections need be neither orthogonal nor central sections of the ellipsoid. Measurement errors are used to adjust the observed plane ellipses so that they are exact sections of the nearest true ellipsoid, whose dimensions and orientation are then found by solution of a system of six linear equations. A solution of the inverse problem is also presented: given a triaxial ellipsoid with known orientation, to determine the shape and orientation of the ellipse on a plane section. The problem is solved by expanding the equation of an ellipsoid with rotated coordinates, then setting one dimension to zero. Also, a method is presented for the projection of a triaxial ellipsoid onto a plane surface. This is solved by taking the derivative of the ellipsoid equation in the direction of the normal to the plane surface. 相似文献
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N. V. Koronovsky G. N. Gogonenkov M. A. Goncharov A. I. Timurziev N. S. Frolova 《Geotectonics》2009,43(5):379-391
An unusual structural paragenesis, complicated by brachyanticlines, is revealed for the first time in the sedimentary cover
of the West Siberian Plate by 3D seismic surveying. These are linear (in plan view) systems of en-echelon arranged low-amplitude
normal faults related to wrench faults in the basement. On different sides off a wrench fault, the planes of normal faults
dip in opposite directions, forming a helicoidal structure that resembles the blades of a propeller. In the section parallel
to the wrench fault, the boundaries of the beds and normal fault planes dip in opposite directions as well. In the section
across the strike of the normal faults converging toward the basement, the beds take the shape of an antiform with a crest
sagged along the normal faults (flower structure). This structural assembly was formed as a result of interference of stress
fields of horizontal shear in the vertical plane (induced by faulting in the basement) and in the horizontal plane (caused
by gravity resistance of the cover). In this case, the displacements along the normal faults develop in both the vertical
and, to a greater extent, horizontal directions, so that the faults in cover are actually characterized by normal-strike-slip
kinematics. The regional N-S-trending compression of the West Siberian Plate is the main cause of shearing along the NW- and
NE-trending faults in the basement, which make up a rhomb-shaped system in plan view. Petroliferous brachyanticlines, whose
axes, notwithstanding tectonophysical laws, are oriented in the direction close to the maximum compression axis, are known
in the large wrench fault zones of Western Siberia. Our experiments with equivalent materials showed that a local stress field
arising at the ends of echeloned Riedel shears within a wrench fault zone may be a cause of the formation of such brachyanticlines.
The progressive elongation of Riedel shears leads to the corresponding elongation of the brachyanticlines located between
their ends. The performed study has shown that the known types of interference of elementary geodynamic settings such as horizontal
shear along the vertical plane + horizontal compression (transpression) and horizontal shear along the vertical plane + horizontal
extension (transtension) may be supplemented by combination of horizontal shears along the vertical and horizontal planes,
resulting in tectonic lamination. By analogy, we propose to name this type of interference of elementary shear settings translamination. Petroliferous helicoidal structures arise in the given geodynamic setting of translamination. 相似文献
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这里研究了VTI(Vertical Transverse Isotropy)介质隐式有限差分(IFD)波场外推算子和VTI介质平面波偏移。在文中设计了VTI介质IFD波场外推算子,将Taylor分析法求得的差分系数,作为初始解,用非线性优化方法迭代求得算子系数。将设计的外推算子频散曲线和偏移脉冲响应与理论解进行了对比分析,验证出外推算子有较高的精度。从各向同性介质平面波偏移理论出发,结合VTI介质IFD波场外推算子,将平面波偏移推广到VTI介质中。对Hess VTI标准模型拟合数据进行偏移,偏移结果验证了平面波偏移在VTI介质中的有效性,以及在加强特定陡倾界面成像方面的优势。并且,与常规VTI介质叠前深度偏移相比,VTI介质平面波偏移在保证成像质量的前提下,大大减少了计算量,为各向异性偏移成像研究提供了新的技术思路。 相似文献
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Conclusions As can be seen from Table 1, the two trend surfaces give considerably different values. Our data were chosen not to fit any
one plane and this is reflected in both of the trend surfaces. The program has been run with different data, and as the data
tend toward a plane both trend surfaces become nearly identical as one would expect.
We conclude that the type of plane to use for trend-surface analysis does indeed depend on the hypotheses of the fitting technique. 相似文献
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C. Lin 《Mathematical Geology》1982,14(5):501-508
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Uniform investigation of hydraulic fracturing propagation regimes in the plane strain model 下载免费PDF全文
The hydraulic fracturing propagation regimes in the plane strain model are uniformly investigated using a numerical method based on the finite element method. The regimes range from toughness‐dominated cases to viscosity‐dominated cases, covering zero leak‐off situations and small leak‐off situations. Unlike the asymptotic solutions, the numerical method is independent of the energy dissipation regimes and fluid storage regimes. The numerical method pays no special attention to the fracture tip, and it simulates fracture tip behaviors by increasing the number of functions in a natural and uniform manner. The numerical method is verified by comparing its results with the asymptotic solutions. The effect of the model sizes on the numerical method is discussed along with the robustness of the numerical method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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The Hellenic arc is the most active seismic region of the transition zone between the African and Eurasian plates. In this rapidly deforming region, the physical state of the crust and upper mantle may vary laterally and vertically. However, a detailed 3D model of the region is lacking. The reliable determination of fault plane solutions is crucial if such a model is to be produced. On this basis, fault plane solutions have been determined from recent microearthquakes and small events to assess their reliability for use in tectonic interpretation. A search algorithm on first motion data and amplitude ratios and also a waveform-matching scheme were employed on data from our temporal network, operated on the western part of the island of Crete. There, a network of 47 three-component digital stations with an aperture of 60 km and an average station spacing of 5 km was operated in 1997. The majority of the shallow microearthquakes under Crete for which fault plane solutions were determined have a near horizontal T-axis oriented essentially E–W. Differences between well determined fault plane solutions from the search algorithm and the waveform-matching technique were significant (strike up to 45°, dip up to 10°, and slip up to 50°). Second, data of small events within the Hellenic subduction zone were obtained from recently installed broadband stations at local and regional distances and inverted for a deviatoric seismic moment tensor. Available solutions from other sources such as the Harvard group, EMSC, or SED show drastic differences in part. Owing to still limited azimuthal station coverage, the resulting fault plane solutions of small events have generally not been well constrained. The observed large variation of fault plane solutions for micoearthquakes and small events poses a caveat to tectonic interpretation in case of using data from a few stations only. 相似文献
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Hsiung Bin-Chen Benson Likitlersuang Suched Phan Khac Hai Pisitsopon Piroon 《Acta Geotechnica》2021,16(6):1923-1938
Acta Geotechnica - Due to tool, time and budget limitations, 2-dimensional analyses of deep excavation are often adopted for engineering practice; thus, the 3-dimensional behaviour is ignored.... 相似文献
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