岩体结构面强度的可靠度分析

基于岩体结构面破坏的Mohr-Coulomb准则和可靠度理论,视结构面和岩块强度参数以及结构面倾角为随机变量,分析了结构面强度参数的变异性对结构面破坏概率的影响,探讨了结构面破坏概率随结构面倾角的变化规律,提出了结构面和岩块破坏概率的计算公式,找出了影响结构面破坏概率的主要因素。结果表明,岩体结构面强度的可靠度分析比传统的定值分析方法更为客观合理。     

试论粘土矿物转化过渡结构

文中论述了一种粘土矿物向另外一种粘土矿物转化过程中存在一个过渡阶段,在这个过渡阶段的矿物结构状态称为过渡结构。本文系统讨论了(1)2∶1结构向1∶1结构转化;(2)2∶1结构向相邻的2∶1结构转化;(3)层链状结构向层状结构转化;(4)多型转化等过渡结构。     

软土地铁车站结构及隧道的三维地震响应分析

建立了软土地铁车站结构及相邻隧道的三维计算模型,研究了其三维地震响应规律,确定了结构的薄弱部位及地震荷载引起结构内力的增幅,分析了隧道对车站结构内力的影响。研究表明：①在距离车站结构端墙1.5倍车站结构横向宽度的横截面,可按平面应变问题分析;②车站结构受力较大的部位有：上柱上端与板结合处、底板跨边与侧墙结合处、底板中跨跨中及车站结构的前端墙;③地震荷载对柱端弯矩的影响最大;④区间隧道的存在削弱了车站结构前后端墙的整体抗震性能。研究成果可为地铁车站结构及隧道的抗震设计提供参考。     

黄土湿陷性的微结构效应

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。     

黄铁矿热电结构

本文提出了半导体矿物热电结构的概念。以黄铁矿为例提出了热电结构的分类命名,金矿床黄铁矿热电结构系列的实例,广泛的标型意义,热电结构测试方法。     

刘家峡水电站扩机工程调压井结构研究

基于三维有限元法,对刘家峡水电站扩机工程调压井结构进行了静力、反应谱分析及非线性有限元分析,评价了结构的荷载效应。首先根据线弹性有限元分析结果,采用拉应力图法对调压井衬砌结构进行了配筋;然后以考虑混凝土开裂的非线性有限元方法校核结构强度和裂缝宽度。通过调整配筋面积,提出了适合于该水电站扩机工程调压井结构的最优结构型式和配筋方案。     

非饱和土的承载结构与岩土广义结构性

鉴于非饱和土的复杂性,经典的3相模型过于简单,不利于分析相间相互作用及正确定义土中应力。将非饱和土视为一种特殊结构,并细分为6相,定义了其承载结构--广义土结构,进而分析了饱和土与非饱和土的主要差异：承载结构和孔隙流体均不同。基于承载结构的共性,提出了一套定性描述土体结构特点的指标--广义结构性,其普遍适用于描述不同土的承载结构特点。结合实际现象,分析了各指标的合理性,指出湿陷的本质是广义土结构的弱化。此后,分析了两种代表性相间相互作用,揭示了中性应力的物理意义,并合理定义了吸应力,最终明确了土骨架总应力就是“有效应力”。     

岩体渗透结构类型的划分及其渗透特性研究

划分岩体渗透结构类型是水利水电工程地质勘察和渗透性评价的重要内容。从岩体结构的控渗作用出发,分析了控制岩体渗透特征的主要因素,即岩性、断裂构造、风化卸荷作用及岩溶作用;提出了岩体渗透结构类型的划分原则,即考虑岩体的各向异性特征。根据岩体的宏观渗透特征,即渗透介质及主要途径,将岩体渗透结构类型划分为5类:散体状渗透结构、层状渗透结构、带状渗透结构、网络状渗透结构、管道状渗透结构。结合工程实例,给出了小浪底渗透结构为层状及带状、三峡工程坝址区岩体渗透结构为散体状、网格状及带状。     

小湾水电站坝址区岩体结构面抗剪强度试验研究

小湾水电站坝址区结构面发育,特别是高陡倾角的节理裂隙和Ⅳ级结构面(f、gm)。因结构面强度控制岩体的强度,故研究坝址区各类结构面的抗剪强度具有十分重要的意义。结构面抗剪强度试验制样难度很大,特别是高陡倾角的结构面,在制样过程中要最大限度地减少对岩体的挠动。为此采用了静态爆破方法,成功解决了制样问题。通过大量的结构面抗剪强度试验研究,提出了小湾电站坝址区各种类型结构面的抗剪强度参数,为小湾电站的设计与施工提供了科学依据。     

表层液化地基中结构与桩惯性相互作用简化分析方法

传统桩基础结构抗震设计中一般认为忽略结构与桩基础相互作用影响使得结构所受惯性作用计算结果偏于保守,但对几次强震中地震动反应谱和桩基础结构震害特征的总结与分析表明,液化作用和结构与桩基础相互作用可能导致桩基础结构惯性作用增强。通过可液化地基中桩基础结构的动力离心模型试验手段,分析了地基液化对结构与桩惯性相互作用的影响,发展了适用于表层液化地基中的结构与桩惯性相互作用的简化计算方法,并利用该方法对文中及Wilson等的离心模型试验进行分析,得到的结构加速度与试验结果吻合较好,从而验证了方法的有效性。     

Plagioclase preferred orientation by TOF neutron diffraction and SEM-EBSD

The lattice preferred orientation (LPO) of an anorthosite (composed of andesine) sampled from a highly deformed anorthositic mylonite (Grenville Province, Quebec) was measured by TOF neutron diffraction and SEM-EBSD. The quantitative texture analysis of neutron data was accomplished by using the Rietveld texture analysis with the WIMV algorithm, implemented in the program package Materials Analysis Using Diffraction (MAUD). The texture calculations of the EBSD data were performed by using the program BEARTEX. Analyses from neutron and electron diffraction data gave similar results if EBSD data are smoothed to account for grain statistics. The principal pole figures show (010) roughly parallel to the rock foliation, (001) poles exhibiting a low angle (25°) to the pole to foliation, and (100) poles close to the Y-direction (perpendicular to the lineation and foliation pole). The [100] crystallographic direction shows a maximum in the lineation direction, [010] directions concentrate near the foliation pole. The geological deformation conditions and the constructed pole figure patterns indicate that the preferred orientation could be attributed to intracrystalline slip dominantly on (010) with [100] as slip direction. Elastic properties, calculated by averaging, document weak anisotropy that has implications for the seismic structure of the lower crust.     

Anisotropic phase transition of rutile under shock compression

Shock recovery experiments for single crystal and powdered specimens of TiO₂ with the rutile structure were performed in the pressure range up to 72 GPa. Single crystal specimens were shocked parallel to [100], [110] and [001] directions. X-ray powder diffraction analysis showed that the amount of -PbO₂ type TiO₂ produced by shock-loading depended strongly on the shock propagation direction. The maximum yield (about 70%) was observed for shock loading to 36 GPa parallel to the [100] direction. In the [001] shock direction, the yield is much smaller than that of the [100] direction. This anisotropic yield was consistent with the observed anisotropy of the phase transition pressure in shock compression measurements. However, transformation to the -PbO₂ type cannot explain the large volume change observed above about 20 GPa. On the basis of the high pressure behavior of MnF₂, we assumed that the high pressure phase was either fluorite or distorted fluorite type and that the phase conversion to the -PbO₂ type was induced spontaneously in the pressure reduction process.We present a displacive mechanism of phase transition under shock compression from the rutile structure to the fluorite structure, in which the rutile [100] is shown to correspond to the fluorite [001] or [110] and the rutile [001] to the fluorite [110]. Direct evidence is obtained by examining the [100] shocked specimen by high resolution electron microscopy.     

Twin formation in hematite during dehydration of goethite

Twin formation in hematite during dehydration was investigated using X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy (TEM). When synthetic goethite was heated at different temperatures between 100 and 800 °C, a phase transformation occurred at temperatures above 250 °C. The electron diffraction patterns showed that the single-crystalline goethite with a growth direction of [001]_G was transformed into hematite with a growth direction of [100]_H. Two non-equivalent structures emerged in hematite after dehydration, with twin boundaries at the interface between the two variants. As the temperature was increased, crystal growth occurred. At 800 °C, the majority of the twin boundaries disappeared; however, some hematite particles remained in the twinned variant. The electron diffraction patterns and high-resolution TEM observations indicated that the twin boundaries consisted of crystallographically equivalent prismatic (100) (010), and (1\(\bar{1}\)0) planes. According to the total energy calculations based on spin-polarized density functional theory, the twin boundary of prismatic (100) screw had small interfacial energy (0.24 J/m²). Owing to this low interfacial energy, the prismatic (100) screw interface remained after higher-temperature treatment at 800 °C.     

氟碳钙铈矿6R2新多型的高分辨电镜研究

用电子衍射和高分辨电子显微镜技术研究了钙稀土氟碳酸盐系列矿物中氟碳钙铈矿及其衍生体的微结构,发现了氟碳钙铈矿的６Ｒ２新多型体,确定了其亚结构晶胞呈六方（Ｈ）对称α＇＝０．４１２ｎｍ,ｃ＇＇＝０．４７１ｎｍ,超结构晶胞呈菱面体（Ｒ）对称,ａ＝０．７１４ｎｍ,ｃ＝８．４７８ｎｍ,可能的空间群为Ｒ３＾－ｃ和Ｒ３ｃ,［１２１０］取向的高分辨结构像显示出该多型体结构单元层沿ｃ轴的有序堆垛及重复周期。［０００     

会聚束电子衍射对葡萄石空间群的辅助测定

利用透射电子显微技术测定了湖北大冶铁山矿床中的微米级葡萄石空间群。选区电子衍射几何构图法分析表明,该矿物系斜方晶系,衍射消光符号为Ｐｎ－－晶胞参数为α＝０．４５８,ｂ＝０．５５５和ｃ＝１．８５３ｎｍ。（１００）和（３０１）方向的会聚束电子衍射花样研究表明,其空间群为Ｐｎｃｍ。     

SAED and HRTEM Investigation of Palygorskite

The microstructure of palygorskite from Longwang Mountain of Xuyu County, Jiangsu Province, was studied by energy dispersive X-ray analysis （EDX）, selected-area electron diffraction （SAED） and high-resolution transmission electron microscopy （HRTEM）. The average composition of the palygorskite studied is （Si7.38A10.62） （A10.96Fe^3＋ 0.62Mg2.86 0.56）Ca0.03K0.06O20（OH）2（OH2）4, which is rich in Mg. Several SAED patterns from a single crystal of palygorskite were obtained with different zone axes. The polymorphs （monoclinic and orthorhombic） are unequivocally distinguished by distant interplanar angles, even though they possess similar sets of d-values. High-resolution images of three principal zones （[010], [100] and [110]） were obtained. The lattice fringes on HRTEM images along [010] have spacings of 0.319 nm. These fringes are interpreted as periodic alterations of two tetrahedral （T） sheets and one octahedral （O） sheet （-TT-O-TT-O-）. We have directly observed trioctahedral and dioctahedral individual palygorskite particles along [100]. They are all presented as dark lines along [001], but the width of dark lines corresponding to trioctahedral crystals （0.913 nm） is twice that of the dioctahedral ones （0.456 nm）. This is because the trans.sites are occupied by cations in trioctahedral palygorskite. The width of dark lines along [110] is 1.024 nm, a bit thinner than the theoretical spacing （1.044 nm）. This is because water molecules quickly leave the structure upon the irradiation by the electron beam.     

Structure of the 30-sectored polygonal serpentine. A model based on TEM and SAED studies

 Polygonal serpentine (PS) from selected serpentinite were studied using transmission electron microscopy. Fiber axis selected-area electron diffraction (SAED) patterns and electron micrographs reveal orthogonal and monoclinic lizardite polytypes. The PS models by Chisholm (1992) and Baronnet et al. (1994) do not fit SAED measurements. Experimental results are matched with calculated diffraction geometry and intensities, as well as with simulated images, indicating inversion of the tetrahedral layer at sector boundaries. The structural relationships between chrysotile and PS are discussed. Two types of 30-sectored PS are distinguished. In “regular PS” the fiber axis is [100], in “helical PS” the fiber axis points into a [uν0] direction with large u value (u≫ν). Helical PS can be regarded as a lizardite analogue of helical chrysotile. Received December 6, 1995/Revised, accepted May 8, 1996     

Olivine [100] normal to foliation: lattice preferred orientation in prograde garnet peridotite formed at high H<Subscript>2</Subscript>O activity,Cima di Gagnone (Central Alps)

Automated electron backscattered diffraction (EBSD) was applied using a scanning electron microscope to obtain lattice preferred orientation (LPO) data for olivine in garnet peridotites of the Central Alps. As a reference frame, the LPOs of enstatite were also investigated. In the garnet peridotite at Cima di Gagnone (CDG), a weak foliation carrying a distinct lineation is present. The lineation is characterized by elongated enstatite, olivine and poikiloblastic garnet. Olivine shows a very unusual LPO with [100] normal to foliation and [001] parallel to lineation. Achsenverteilungsanalyse (AVA) maps demonstrate that [001] of olivine grains corresponds quite well to their maximum length axes which are preferentially parallel to the lineation. Numerous planar hydrous defects within (001) planes of olivine are marked by palisades of ilmenite rods and show a preferred orientation normal to lineation. Calculated P-wave velocities for CDG are fastest (8.32 km s^у) normal to foliation with a relatively low anisotropy (2.9%). Compared to mantle peridotites with the usual (010)[100] LPO where the fastest Vp direction is towards the lineation, the relationship between flow geometry and seismic anisotropy is significantly different at CDG. Several mechanisms for the formation of the LPO type at CDG are considered, with glide possible on (100)[001] of olivine. On the basis of field data as well as petrographic and petrologic evidence, it has been demonstrated that the CDG garnet peridotite formed by prograde metamorphism from a hydrous protolith at pressures and temperatures of about 3.0 GPa and 750 °C, respectively. The CDG LPO is interpreted to have formed during hydrous subduction zone metamorphism. The same interpretation may hold for the previously investigated olivine LPO at Alpe Arami, which is similar to that at the nearby CDG. The observed anomalous LPO is no proof for ultradeep (>3.0 GPa) conditions.     

天然钒钛磁铁矿中出溶现象的高分辨电镜观察

利用高分辨电子显微镜及微区X射线能谱成分测定的方法,对含钒的天然磁铁矿的精细结构进行了研究。结果表明,[110]方向的高分辨像清楚地显示钒钛磁铁矿在磁铁矿基体中以共(110)面紧密连生的方式与基体共生,形成波状连生体。这种成份调制波结构表明它们是出溶产物。     

Comparison of the surface structure of the tetrahedral sheets of muscovite and phlogopite by AFM

 The surface structure of the tetrahedral sheet of dioctahedral mica muscovite was compared to that of the tetrahedral sheet of trioctahedral mica phlogopite using atomic force microscopy (AFM). AFM revealed distinct structural differences between the tetrahedral sheet surfaces of the two micas. The hexagonal ring in the AFM image of muscovite elongates in the [3 1 0] direction, and the groove runs perpendicular to the [3 1 0] direction. On the phlogopite surface, the hexagonal ring contracts slightly in the a axis direction, but the groove is not apparent. These results were consistent with the bulk structure data of the two micas determined by X-ray diffraction (XRD). The degree of surface relaxation was much larger in muscovite than in phlogopite. In muscovite, the interlayer K reduces the amount of tetrahedral rotation that actually occurs, since the interlayer K is too large for its hexagonal hole after full tetrahedral rotation. Thus, it is naturally expected that muscovite will show more tetrahedral rotation after removal of the interlayer K. It is also expected that muscovite will show more tilting of SiO₄ tetrahedra after cleaving, since an attractive force between the hydrogen in the OH group and the lower basal oxygen should be in operation, due to the decreased distance between them following interlayer K removal. Received: 14 March 2000 / Accepted: 29 July 2000