黄土湿陷性的微结构效应   总被引：21，自引：8，他引：13  

胡瑞林  官国琳  李向全 《工程地质学报》1999,7(2):161-167

土结构是一种物质状态,可以层次式的概念模型加以确定。从图象处理角度,提出了微结构定量研究的技术路线,确定了结构要素的量化方法。通过分形结构分析,探讨了天然结构和压力对黄土湿陷性的影响、水与土样之间的作用规律及其湿陷效应,提出了分形结构的湿陷性控制机理。  相似文献   

The Magnetic Properties and Crystal Chemistry of Oxide Spinel Solid Solutions     

Richard J. Harrison  Andrew Putnis 《Surveys in Geophysics》1998,19(6):461-520

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辽河群变质泥质岩中变质重结晶作用和变形作用的关系   总被引：10，自引：3，他引：7  

李三忠  刘永江 《岩石学报》1998,14(3):351-365

辽河群变泥质岩中变斑晶种类繁多,有的具多个世代。同位素年代学证据表明它们都形成于吕梁变质期。通过２０００多块薄片的详细显微构造分析,将吕梁变质期分成四个变质阶段。变斑晶微构造揭示Ｍ１发生于变形前埋藏过程中,Ｍ２、Ｍ３属进变质阶段,Ｍ４为退变阶段。变斑晶在各变质阶段以完整或不完整的基本结晶序列周期性地出现,成核具阶段性,生长既有阶段性的又有具连续性的。变斑晶在不同的变形条件下,具有不同的变形行为,如旋转与非旋转性。变斑晶的时空分布规律揭示,Ｍ２期间垂向递增变质带与Ｄ１伸展构造样式密切相关;Ｍ３期间侧向递增变质带样式与收缩挤压褶皱样式一致。  相似文献   

长春季冻区路基土微观孔隙特征的定量评价   总被引：1，自引：0，他引：1  

赵安平  王清  李杨  车茜 《工程地质学报》2008,16(2):233-238

路基冻害一直是困扰东北季冻区道路建设的一个重要问题。长春冬季天气寒冷,在温度梯度作用下路基土中水分产生迁移和聚集,引起路基冻胀。春季路基解冻,集聚的冰晶体融化,路基土处于饱和或过饱和状态,承载力极低,在交通车辆作用下发生路面鼓包、弹簧、断裂和翻浆冒泡等现象,给交通运输和经济建设带来极大的危害。孔隙是水分迁移的主要通道,是影响路基冻胀主要因素之一,其特征决定土体的冻胀敏感性。本文利用WD-5配置联机图象处理系统的电子显微镜,通过图像定量分析系统,对长春季冻区路基土的微观孔隙作了定量评价。经过分析得出:3个土样孔隙直径均是小于5m的占主导地位,都具备冻胀条件;试样水平和垂直两个方向的孔隙分布较均匀,孔隙为辐射状或网状结构,多为扁圆和等轴形状;孔隙形态分维数分析认为,分维数高,大孔隙含量多,孔隙分布比较简单,在研究范围内,有利于水分迁移,冻胀性较强。  相似文献   

Influence of microfossils and pyrites on the behaviour of oceanbed sediments     

G. Rajasekaran   《Ocean Engineering》2006,33(3-4):517-529

An attempt has been made to investigate the microfabric and mineralogical features of marine sediments collected from the north-east coastal region of Singapore. A limited laboratory studies on shear strength, consolidation and chemical analysis were carried out to examine the geotechnical characteristics of marine sediments. Emphasis has been focussed on the microfabric aspects of microfossils (diatom) and pyrite, and their influence on the soil properties. Test results indicated the predominant presence of microfossils (diatom) and pyrite, and their impact on the marine sediments behaviour has been discussed briefly. The abundant presence of microfossils results in an increase in strength, compressibility and hydraulic conductivity due to the presence of large voids between the skeleton structures.  相似文献   

大弹涂鱼血液的研究   总被引：12，自引：0，他引：12  

曹伏君  李长玲  刘楚吾 《海洋湖沼通报》2000,(2):11-15

本文报道了大弹涂鱼外周血胞的显微结构,血涂片经过染色,可鉴定出红细胞、单核细胞、淋巴细胞、血栓细胞和中性粒细胞,未发现酸性粒细胞和碱性粒细胞。红细胞数量多,圆形,具圆核。血栓细胞体积最小,单核细胞体积最大,淋巴细胞有大小两种：大淋巴细胞和小淋巴细胞。还见到红细胞、大、小淋巴细胞可在外周血液中通过直接分裂产生。此外,血液中还观察到分解、解体状态的红细胞。  相似文献   

Spherulitic omphacite in pseudotachylytes: Microstructures related to fast crystal growth from seismic melt at eclogite-facies conditions     

《Chemie der Erde / Geochemistry》2014,74(3):407-418

The microstructures and microtexture of omphacite spherulites from an eclogite-facies pseudotachylyte from central Zambia was studied by electron backscattered diffraction and transmission electron microscopy. The spherulitic growth is characteristic for fast growth rates at high undercoolings resulting from quenching a melt of seismic origin to the eclogite-facies conditions. Its preservation constrains that no significant deformation was present after the seismic event and during uplift. The analysis of grain misorientations in spherulites indicates – in addition to the overall radial alignment of grains – that crystallization took place in a highly viscous medium, which does not allow grain reorientation during growth. The microstructure of omphacite is diverse and ambiguous: Grain contacts appear both curved and with 120° triple junctions with few recrystallized grains. Dislocations are frequent, but heterogeneously distributed and occur in dislocations networks, subgrain boundaries and as free dislocations with locally high densities. Planar defects (chain multiplicity faults parallel (0 1 0) ending at partial dislocations) are abundant, while twinning parallel to (1 0 0) is rare. Anti-phase domains with variable domain sizes within a single grain and the disappearance of domain walls around the planar defects constrain that most of the microstructure must be formed during or shortly after crystallization.Omphacite microstructures are commonly discussed as result of deformational stresses due to a tectonic forcing. Here, we hypothesize that thermal stress during growth also can provide a feasible explanation for this melt-grown omphacite followed with partial recovery under static conditions. The observation does not exclude repeated stress loading of the shear veins in general, but suggest that only the latest seismic event is preserved in the studied samples as fine-grained texture of the spherulites. Moreover, anti-phase domain sizes constrain that the rock must be uplifted rather shortly after the seismic event.  相似文献   

The microstructure of polar ice. Part II: State of the art     

《Journal of Structural Geology》2014

An important feature of natural ice, in addition to the obvious relevance of glaciers and ice sheets for climate-related issues, is its ability to creep on geological time scales and low deviatoric stresses at temperatures very close to its melting point, without losing its polycrystalline character. This fact, together with its strong mechanical anisotropy and other notable properties, makes natural ice an interesting model material for studying the high-temperature creep and recrystallization of rocks in Earth's interior. After having reviewed the major contributions of deep ice coring to the research on natural ice microstructures in Part I of this work (Faria et al., 2014), here in Part II we present an up-to-date view of the modern understanding of natural ice microstructures and the deformation processes that may produce them. In particular, we analyze a large body of evidence that reveals fundamental flaws in the widely accepted tripartite paradigm of polar ice microstructure (also known as the “three-stage model,” cf. Part I). These results prove that grain growth in ice sheets is dynamic, in the sense that it occurs during deformation and is markedly affected by the stored strain energy, as well as by air inclusions and other impurities. The strong plastic anisotropy of the ice lattice gives rise to high internal stresses and concentrated strain heterogeneities in the polycrystal, which demand large amounts of strain accommodation. From the microstructural analyses of ice cores, we conclude that the formation of many and diverse subgrain boundaries and the splitting of grains by rotation recrystallization are the most fundamental mechanisms of dynamic recovery and strain accommodation in polar ice. Additionally, in fine-grained, high-impurity ice layers (e.g. cloudy bands), strain may sometimes be accommodated by diffusional flow (at low temperatures and stresses) or microscopic grain boundary sliding via microshear (in anisotropic ice sheared at high temperatures). Grain boundaries bulged by migration recrystallization and subgrain boundaries are endemic and very frequent at almost all depths in ice sheets. Evidence of nucleation of new grains is also observed at various depths, provided that the local concentration of strain energy is high enough (which is not seldom the case). As a substitute for the tripartite paradigm, we propose a novel dynamic recrystallization diagram in the three-dimensional state space of strain rate, temperature, and mean grain size, which summarizes the various competing recrystallization processes that contribute to the evolution of the polar ice microstructure.  相似文献   

黑方台马兰黄土固结条件下孔隙变化特征   总被引：1，自引：0，他引：1  

罗浩  伍法权  常金源  许江波  包含 《工程地质学报》2014,22(5):845-850

甘肃临夏地区的黑方台由于长期的农业灌溉导致台缘滑坡频发,整个台面普遍下沉3m以上。文章通过原状黄土的增湿固结实验、压汞试验和环境扫描电镜等对黑方台顶部和底部的原状黄土进行孔隙特征的分析。黑方台顶部黄土颗粒排列极为疏松、孔隙较大、黏土含量较低。底部黄土排列较为紧密,具有一定的孔隙,黏土含量较高。顶部黄土在固结实验中,21%含水量的黄土发生孔隙比突降,黄土的微观结构强度此时迅速减小或丧失。然而底部黄土没有发生明显的突变,水敏性不强。利用压汞试验确定了黑方台顶部黄土的孔隙主要压缩区间为孔径大于100m、孔径5～20m之间; 底部黄土的孔隙主要压缩区间为孔径大于100m、孔径1～10m之间。而且孔径小于0.1m的孔隙随含水量的升高具有增加的趋势。  相似文献   

The lateral boundary of a metamorphic core complex: The Moutsounas shear zone on Naxos,Cyclades, Greece     

《Journal of Structural Geology》2013

We describe the structure, microstructures, texture and paleopiezometry of quartz-rich phyllites and marbles along N-trending Moutsounas shear zone at the eastern margin of the Naxos metamorphic core complex (MCC). Fabrics consistently indicate a top-to-the-NNE non-coaxial shear and formed during the main stage of updoming and exhumation between ca. 14 and 11 Ma of the Naxos MCC. The main stage of exhumation postdates the deposition of overlying Miocene sedimentary successions and predates the overlying Upper Miocene/Pliocene conglomerates. Detailed microstructural and textural analysis reveals that the movement along the Moutsounas shear zone is associated with a retrograde greenschist to subgreenschist facies overprint of the early higher-temperature rocks. Paleopiezometry on recrystallized quartz and calcite yields differential stresses of 20–77 MPa and a strain rate of 10⁻¹⁵–10⁻¹³ s⁻¹ at 350 °C for quartz and ca. 300 °C for calcite. Chlorite geothermometry of the shear zone yields two temperature regimes, 300–360 °C, and 200–250 °C. The lower temperature group is interpreted to result from late-stage hydrothermal overprint.  相似文献