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131.
The 2004 Chuetsu earthquakes of Niigata (Japan) triggered numerous landslides, and the most widespread types of landslides
were highly disrupted, relatively shallow slides and soil (debris) flows. This paper presented a method to evaluate slope
instability using Newmark displacement on a pixel-by-pixel basis in a given area. The proposed method was able to integrate
Newmark displacement modeling and Monte Carlo simulations within geographical information systems. In the modeling, an empirical
attenuation relationship was utilized to calculate Arias intensity over this study area, and the variability of geotechnical
parameters was taken into account to calculate coseismic landslide displacement. Before deriving the displacement from related
inputs, the Monte Carlo simulations ran 1,500 times and generated 1,500 displacement values for each grid cell, and then means
and standard deviations of displacement were calculated and probabilistic distributions can be obtained. Finally, given 10 cm
as a threshold value of displacement, estimated probabilities of displacement exceeding 10 cm were shown as a map of seismic
landslide hazards. The resulting hazard map was classified into four categories from very low to high level. 相似文献
132.
冀北榆树沟煤矿区褐煤地下气化地质条件分析 总被引:1,自引:0,他引:1
通过对冀北沽源县榆树沟煤矿白芈系青石砬组含煤地层地质条件进行分析,认为仵该矿区进行煤炭地下气化是可行的。研究区构造简单,为一轴向近东西向的舒缓向斜,主要煤层厚度大,最大平均厚度为24.31m。可采煤层顶板多为泥岩、炭质泥岩,尤其是煤系上覆的“三趾马红土”层,对气体有良好的圈闭作用。由于褐煤的灰分含量高,26%~49.03%,地下气化时对煤层顶板影响小,主要煤层埋藏浅200—300m,水文地质条件简单,根据诸多因素分析认为该矿区适合进行褐煤地下气化开采。 相似文献
133.
The problem of arsenic (As) poisoning in the upper deltaic plain of the Ganga-Bhagirathi river system in the Bengal Basin
of West Bengal, India is an alarming issue. Four blocks (Kaliachak-1, 2, 3 and English Bazar) of Malda district, West Bengal
were critically studied. Geomorphologically, the area exhibits three terraces: the present Youngest terrace (T0-terrace), the Older Shaugaon Surface (T1-terrace) and the Oldest Baikunthapur Surface (T2-terrace). On the basis of numerous measurements, including As-content, pH, DO, specific conductivity and salinity, it was
observed that maximum As-content beyond the permissible limit (0.05 mg/L, Indian standard) occurs within a depth range of
10–30 m with a non-linear distribution pattern. Variance test also found that a block effect was highly significant in an
As-distribution pattern. Mean arsenic level of Kaliachak block-1 is 0.2253 mg/L, followed by Kaliachak-2 with arsenic level
0.1923, Kaliachak-3 with arsenic level 0.1755 and English Bazar with arsenic level 0.1324. The arsenious belt lies mainly
within the Older terrace (T1). The very recent flood plain deposits of silvery white, fine sands lying very close to the Ganga River margin do not contain
significant amounts of As. Elevated As-concentration in the ground water was observed in alluvial sands, grayish white to
brownish in color and occurring away from the Ganga margin. The Oldest terrace (T2) further away from the Ganga margin (e.g.
English Bazar) and Barind surface contains less arsenic. Barind surface acts as a hard capping with ferruginous sands and
lateritic concretions-chocolate, mottled and purple brown in color-occurring northeast of the studied area. Arsenic content
of ground water in the same locality within a radius of ∼ 20 m varies within wide limits. Thus, it poses problem to delineate
its distribution pattern. Such a patchy occurrence possibly could not be explained satisfactorily solely by geomorphology.
Chemical analysis of aquifer clay samples of the cores shows a maximum Ascontent of up to 3 mg/kg, whereas the bulk samples
(sandclay mixture) of the cores contain a maximum of 17 mg/kg As-value. Therefore, it is not always true that clay contains
elevated As-value. 相似文献
134.
位于乌鲁木齐市南湖路以西的煤炭采空区面积达67 100.5m^2,区内构造从南到北主要由八道湾向斜和七道湾背斜组成,地层产状变化不大。该矿区开采较深,且采空区塌陷区有明显的地下水活动迹象。在对深孔大体积采空区注浆时,比较各种常见注浆治理方法,均存在不同的制约因素,故决定采用灌浆爆破压密法对采空区进行压实加固。经现场爆破试验,该区重复爆破次数在3~5次左右。灌浆爆破压密处理后,对不同土层进行取样对比分析,得到其相应密度(增加)及空隙比(减少)的变化分别为:杂填土14.1%,-7.9%;素填土5.9%,-3.3%;塌落煤层7.8%,-7.7%。根据压缩数据及现场测量,处理后的土体沉降2~4m,部分空体地段的沉降量达10~20m,治理效果明显。 相似文献
135.
针对野外数据采集参数对分辨率的影响,对资料处理过程中静校正、反褶积、速度分析、Q补偿及谱白化等几个重要模块原理进行分析,指出在高速岩层中数据采集,应采用小药量激发,小道距,小排列,全三维,不组合、单点数字检波器接收。高密度多点采集,能够充分保护有效地质信息的高频成份,在更大范围内满足高分辨地震勘探的要求。资料处理过程中,在保证同相叠加和高信噪比的前提下,采用提高分辨率的模块以弥补地震波在传播过程中损失的高频成份。实践证明通过高保真、宽频带数据采集和高信噪比前提下的高分辨率数据处理,完全能够为矿井采掘提供高精度地震勘探资料。 相似文献
136.
受限于地震波主波长的1/4,常规地震处理难以分辨较薄煤层。基于模型的波阻抗反演虽然克服了厚、薄煤层计算问题.但因难以得到准确的高频部分,很多情况下反演结果的精度和分辨率往往不能满足地质预测的要求。小波边缘分析建模波阻抗反演方法是从地震数据中提取地震特征参数,用于建模并参与迭代反演。该方法即可以弥补反演过程中高频成分的误差,减少对钻井数据的依赖程度,得到较为合理的初始模型,又可提高反演的精度和分辨率.使反演结果更好的反映实际地下地质情况。利用该方法,对大井-将军庙及新疆红沙泉2个勘探区的侏罗系中统西山窑组含煤地层进行波阻抗反演,反演结果与钻井资料进行比较,其中大井一将军庙0802及0809号孔单煤层厚度误差分别为3%、8%.新疆红沙泉多煤层厚度及煤层之间的夹层厚度预测结果除B6煤层误差较大外,其它误差均小于7%.可见该反演方法的计算结果比较准确。 相似文献
137.
138.
Patterns of crystallographic preferred orientation are referred to as texture. The specific subject of texture analysis is
the experimental determination and interpretation of the statistical distribution of orientations of crystals within a specimen
of polycrystalline material, which could be metals or rocks. The objective is to relate an observed pattern of preferred orientation
to its generating processes and vice versa. In geosciences, texture of minerals in rocks is used to infer constraints on their
tectono-metamorphic history. Since most physical properties of crystals, such as elastic moduli, the coefficients of thermal
expansion, or chemical resistance to etching depends on crystal symmetry and orientation, the presence of texture imparts
directional properties to the polycrystalline material.
A major issue of mathematical texture analysis is the resolution of the inverse problem to determine a reasonable orientation
density function on SO(3) from measured pole intensities on
, which relates to the inverse of the totally geodesic Radon transform. This communication introduces a wavelet approach into
mathematical texture analysis. Wavelets on the two-dimensional sphere
and on the rotational group SO(3) are discussed, and an algorithms for a wavelet decomposition on both domains following the
ideas of Ta-Hsin Li is given. The relationship of these wavelets on both domains with respect to the totally geodesic Radon
transform is investigated. In particular, it is shown that the Radon transform of these wavelets on SO(3) are again wavelets
on
. A novel algorithm for the inversion of experimental pole intensities to an orientation density function based on this relationship
is developed. 相似文献
139.
Inversely-Mapped Analytical Solutions for Flow Patterns around and within Inclined Elliptic Inclusions in Fluid-Saturated Rocks 总被引:1,自引:0,他引:1
Chongbin Zhao Bruce E. Hobbs Alison Ord Shenglin Peng Liangming Liu 《Mathematical Geosciences》2008,40(2):179-197
In this paper, an inverse mapping is used to transform the previously-derived analytical solutions from a local elliptical
coordinate system into a conventional Cartesian coordinate system. This enables a complete set of exact analytical solutions
to be derived rigorously for the pore-fluid velocity, stream function, and excess pore-fluid pressure around and within buried
inclined elliptic inclusions in pore-fluid-saturated porous rocks. To maximize the application range of the derived analytical
solutions, the focal distance of an ellipse is used to represent the size of the ellipse, while the length ratio of the long
axis to the short one is used to represent the geometrical shape of the ellipse. Since the present analytical solutions are
expressed in a conventional Cartesian coordinate system, it is convenient to investigate, both qualitatively and quantitatively,
the distribution patterns of the pore-fluid flow and excess pressure around and within many different families of buried inclined
elliptic inclusions. The major advantage in using the present analytical solution is that they can be conveniently computed
in a global Cartesian coordinate system, which is widely used in many scientific and engineering computations. As an application
example, the present analytical solutions have been used to investigate how the dip angle of an inclined elliptic inclusion
affects the distribution patterns of the pore-fluid flow and excess pore-fluid pressure when the permeability ratio of the
elliptic inclusion is of finite but nonzero values. 相似文献
140.
Andrea Lami Frank Niessen Piero Guilizzoni Julieta Masaferro Claudio A. Belis 《Journal of Paleolimnology》1994,10(3):181-197
We use palaeolimnological techniques to reconstruct the eutrophication history of a volcanic lake (Lake Albano, central Italy) over the past three centuries. The presence of annual varves down to the bottom of the core (c. 1700 A.D.) indicated the lack of bioturbation and likely long-term meromixis. Sedimentation rates were estimated by varve counts (calcite/diatom couplets), indicating a mean rate of 0.15 cm yr–1. The reconstruction of eutrophication was traced using past populations of algal and photosynthetic bacteria (through their fossil pigment), and geochemistry, as well as fossil remains of chironomids. Phaeophorbidea and the red carotenoid astaxanthin were used to detect past zooplankton development.The first sign of trophic change related to human activities is datedc. 1870 A.D. From that period onward a sharp increase of authigenic CaCO3, nitrogen, N:P ratio, and dinoxanthin, a characteristic carotenoid of Chrysophyceae and Dinophyceae, is observed.Chironomid analyses showed the near absence of a deep water fauna throughout the core length. The populations of chironomid larvae are restricted to oxygenated littoral zones. In fact, the few fossil remains found are primarily of littoral origin, representing shallow water midges that were transported to profundal waters. The reduction of total chironomid in the uppermost layers of the core is to be related to human land uses. 相似文献