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1.
The structure of coesite has been determined at ten pressures up to a maximum of 8.68 GPa by single-crystal X-ray diffraction.
The dominant mechanism of compression is the reduction of four of the five independent Si–O–Si angles within the structure.
There is no evidence of the fifth linkage, Si1–O1–Si1, deviating from 180°. Some Si–O bond distances also decrease by up to
1.6% over the pressure range studied. The pattern of Si–O–Si angle reduction amounts to a rotation of the Si2 tetrahedron
around the [001] direction. This rotation induces significant internal deformation of the Si1 tetrahedron. Comparison of the
experimental data with rigid-unit distance least-squares simulations of coesite suggests that this pattern of compression,
the anomalous positive values of both s23 and K′′ in the equation of state of coesite, its high elastic anisotropy and the unusual straight Si1–O1–Si1 linkage within
the structure are all consequences of the connectivity of the tetrahedral framework.
Received: 11 July 2002 / Accepted: 14 January 2003
Acknowledgements The help of Christian Baerlocher of ETH Zurich in providing both the DLS-76 software and advice in its use is gratefully
acknowledged, as are discussions with Paul Ribbe of Virginia Tech and the comments of two anonymous reviewers. The data analysis
was supported by the National Science Foundation under grant EAR-0105864 to N.L. Ross and R.J. Angel. 相似文献
2.
中国大陆科学钻探主孔2000米以上脆性变形构造应力场 总被引:6,自引:6,他引:6
在主孔2000米之内,存在复杂的脆性破裂系统和构造应力场。根据其充填物的特征,可划分为由石英、方解石和绿泥石等矿物充填的微破裂,发育石英、方解石等矿物薄膜或擦痕线理的微破裂和既无矿物充填、也无矿物薄膜的微破裂等3种不同类型的脆性应变现象,它们依次代表早、中、晚和深、中、浅3个不同构造层次的脆性变形。初步分析表明脆性变形阶段存在有以南东东-北西西向为主导的挤压作用、北东-南西向的区域挤压作用、南北向挤压作用和垂向伸展作用等4期构造应力场。郯庐断裂东侧的现代构造应力场在区域上具有极大的稳定性。在脆性和脆-韧性转换带,制约苏鲁高压-超高压变质带侵位的主导应力作用方式为自南东东往北西西方向的挤压,它在时间和空间上具有一定的稳定性。 相似文献
3.
Naïma AbouAli Mohamad Hafid El Hassane Chellaï Mohamed Nahim Mahmoud Zizi 《Comptes Rendus Geoscience》2005,337(14):1267-1276
Seismic reflection profiles from the Ifni/Tan-Tan Atlantic margin of southern Morocco, interpreted in the light of well data and field geology from the Western Anti-Atlas, allowed us to establish the seismostratigraphic framework of the syn-rift series and to reveal (i) a compressional structural style in the pre-Triassic basement similar to that established in the adjacent outcropping onshore basement but with an opposed western vergence, (ii) the importance of inherited anterior structures in the formation of Triassic-Liassic rift structures and (iii) an east–west propagation of these rift structures. To cite this article: N. AbouAli et al., C. R. Geoscience 337 (2005). 相似文献
4.
BJRN K.ALSBERG 《地理学报(英文版)》1993,(3)
A general framework for manipulating spectra as functions in traditional multivariate methods such asPCA and PLS is described.The functional representation is very convenient for compression,ensuringsmoothness and continuity.There are two fundamentally different types of representations:(a)byfunctions and(b)by function coefficients.The use of coefficients is the most practical way of analysis. 相似文献
5.
Sudhir Kumar Tewatia Pratima Rani Bose Asuri Sridharan Sunanda Rath 《Geotechnical and Geological Engineering》2007,25(2):239-255
It is shown that time compression curve obtained from one-dimensional consolidation curve in the laboratory may include six
phases. These are initial compression, first primary compression, transition from first primary compression to second primary
compression, second primary compression, and transition from second primary compression to creep and lastly creep. This paper
attempts to identify the quantitative beginnings and characteristics of these phases. A mathematical characteristic of all
the soils that follow primary consolidation as per Terzaghi’s one dimensional consolidation theory is derived. It is known
as the constant of primary consolidation. It is used to study the beginning of secondary consolidation and its effects on
primary consolidation. Another characteristic of soils for creep and total absence of primary compression is derived. Methods
are suggested for the determination of coefficients of Primary and Secondary consolidations and the compression index. 相似文献
6.
珠江三角洲软土微结构的定量研究 总被引:4,自引:0,他引:4
对用不同长度的PVC管在珠海和广州两地采得的淤泥样柱施于一定荷载,然后在扫描电镜下研究软土受压后在样柱垂深方向上的微结构变化,并将样品的微结构照片扫描,在计算机内进行量化处理。结果表明,样品的孔隙分布分维差随着离施压点距离的增加而逐渐减小,从而得到两者的关系方程。据此,可了解在一定荷载下应力在软土层中向下的衰减趋势。文章还对软土的天然含水量和围压对压缩变形的影响作了初步的讨论。 相似文献
7.
专题制图中,所收集到的数据经常是单因素的,而在专题地图上却往往需要把多个单因素专题数据进行综合分类来表示。本文中,采用Fuzzy-Grey局势决策(下简称F-G决策)来研究多因素专题数据的综合分类问题,把“数据的模糊性”引入到灰色局势决策之中,根据不同情况,讨论各局势上效果测度中模糊隶属度确定的建模方法,在合适的隶属函数的基础上,在计算机上对实例分类进行程序运行,获得满意的结果。研究表明应用该方法在专题制图中对多因素数据进行综合分类是一种有效的手段。 相似文献
8.
9.
Clayey sand can be considered as a composite matrix of coarse and fine grains. The interaction between coarser and finer grain matrices affects the overall stress–strain behavior of these soils. Intergranular void ratio, es (which is the void ratio of the coarser grain matrix) can be utilized as an alternative parameter to express the compressive response of such soils. Oedometer tests conducted on reconstituted kaolinite–sand mixtures indicate that initial conditions, percentage of fines, and stress conditions influence the compression characteristics evidently. Tests showed that, up to a fraction of fines, which is named as transition fines content (FCt), compression behavior of the mixtures is mainly controlled by the sand grains. When concentration of fines exceeds FCt, kaolinite controls the compression. It was found that FCt varies between 19% and 34% depending on the above mentioned factors. This range of fines content is also consistent with various values reported in literature regarding the strength alteration. Performed direct shear tests revealed that there is also a close relationship between transition fines content and shear strength, which is harmonic with the oedometer test results. 相似文献
10.