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71.
Values of the complete adiabatic elastic tensor for single-crystal chrome-diopside (a monoclinic pyroxene mineral) are presented from 298 to 1,300 K. The data were obtained using resonant ultrasound spectroscopy (RUS). They are the first published results for the temperature T dependences of the 13 individual elastic constants C
ij
of any clinopyroxene mineral. Each C
ij
is appropriately described by a linear function in T throughout the range of T. Values for each (∂C
ij
/∂T)
P
in GPa K−1 are as follows: C
11, −0.0291; C
22, −0.0248; C
33, −0.0179; C
44, −0.0103; C
55, −0.0077; C
66, −0.0152; C
12, −0.0119; C
13, −0.0064; C
23, 0.0000; C
15, 0.0025; C
25, 0.0022; C
35, −0.0046; and C
46, 0.0026. Values of (∂M/∂T)
P
in GPa K−1, where M represents an isotropic bulk property calculated from the C
ij
data, are as follows: adiabatic bulk modulus K
S
, −0.0123; isothermal bulk modulus K
T
, −0.0178; and shear modulus G, −0.00998. Some diopside derivatives, notably (∂K
S
/∂T)
P
, (∂K
T
/∂T)
P
, and (∂V
P
/∂T)
P
, where V
P
is the compressional wave velocity, have smaller magnitudes than all other minerals of importance in Earth’s mantle, thus, confirming predictions from systematics studies. We find several dimensionless quantities for this monoclinic mineral have normal values compared to other mantle minerals. Further, αK
T
(α is the volume coefficient of thermal expansion) for diopside is approximately independent of both T and volume V at elevated temperature, so its equation of state is accurately expressed in simplified form. 相似文献
72.
Quantifying Damage, Saturation and Anisotropy in Cracked Rocks by Inverting Elastic Wave Velocities 总被引:1,自引:0,他引:1
Alexandre Schubnel Philip M. Benson Ben D. Thompson Jim F. Hazzard R. Paul Young 《Pure and Applied Geophysics》2006,163(5-6):947-973
Crack damage results in a decrease of elastic wave velocities and in the development of anisotropy. Using non-interactive
crack effective medium theory as a fundamental tool, we calculate dry and wet elastic properties of cracked rocks in terms
of a crack density tensor, average crack aspect ratio and mean crack fabric orientation from the solid grains and fluid elastic
properties. Using this same tool, we show that both the anisotropy and shear-wave splitting of elastic waves can be derived.
Two simple crack distributions are considered for which the predicted anisotropy depends strongly on the saturation, reaching
up to 60% in the dry case. Comparison with experimental data on two granites, a basalt and a marble, shows that the range
of validity of the non-interactive effective medium theory model extends to a total crack density of approximately 0.5, considering
symmetries up to orthorhombic. In the isotropic case, Kachanov's (1994) non-interactive effective medium model was used in
order to invert elastic wave velocities and infer both crack density and aspect ratio evolutions. Inversions are stable and
give coherent results in terms of crack density and aperture evolution. Crack density variations can be interpreted in terms
of crack growth and/or changes of the crack surface contact areas as cracks are being closed or opened respectively. More
importantly, the recovered evolution of aspect ratio shows an exponentially decreasing aspect ratio (and therefore aperture)
with pressure, which has broader geophysical implications, in particular on fluid flow. The recovered evolution of aspect
ratio is also consistent with current mechanical theories of crack closure. In the anisotropic cases—both transverse isotropic
and orthorhombic symmetries were considered—anisotropy and saturation patterns were well reproduced by the modelling, and
mean crack fabric orientations we recovered are consistent with in situ geophysical imaging.
Our results point out that: (1) It is possible to predict damage, anisotropy and saturation in terms of a crack density tensor
and mean crack aspect ratio and orientation; (2) using well constrained wave velocity data, it is possible to extrapolate
the contemporaneous evolution of crack density, anisotropy and saturation using wave velocity inversion as a tool; 3) using
such an inversion tool opens the door in linking elastic properties, variations to permeability. 相似文献
73.
支护结构位移对侧土压力影响的计算分析 总被引:1,自引:0,他引:1
针对传统土压力理论在应用中的不足,提出一种基于弹性地基理论的土压力计算方法,可充分考虑墙体对土压力重分布的影响。 相似文献
74.
基于Maxwell和Kelvin流变模型,以延续时间与松弛期的比值,即松弛数,作为衡量指标,对地壳、上地幔不同层次的变形属性进行了判别。结果表明,除软流圈地幔主要为粘性流动外,其上各层的情况是:在漫长的地质过程中,不仅岩石圈地幔和下地壳属于粘性,上地壳也有可能处于粘性流动状态;在延续数十年的情况下,上地壳以及岩石圈地幔都可能呈弹性状态;延续时间介乎二者,通常上地壳为弹性,下地壳和岩石圈地幔为粘性或滞弹粘性。此外,还结合变形属性的判别,就岩石圈地幔的流动和板内的驱动力远程传递等问题进行了讨论 相似文献
75.
断层地震孕震的椭圆形区域及其前兆规律 总被引:2,自引:2,他引:2
首先运用岩石介质的损伤本构关系式和断层地震的简单力学模型,讨论了断层和围岩介质系统的相互作用及其失稳过程,通过差分计算,得到了与地震变形和声发射等有关的前兆序列曲线,然后根据实际断层带滑移与错动的分布规律,通过计算机模拟出断层地震的椭圆形孕震区并此解释了P波初动分布规律。 相似文献
76.
77.
78.
79.
针对声电效应测井问题,提出了一种全波列数值模拟方法.该方法忽略声电效应测井 时转换电场对声场的影响,并将电场视为似稳场.采用点声源模型,依据Biot理论得出了井外 孔隙介质声场的表达式,运用这些表达式和似稳电场近似方法,导出了声电效应测井时转换 电场的计算公式.在计算出的转换电场波形中,有伴随斯通利波的电场、伴随纵波和横波的 电场、和临界折射电磁波场.在25kHz以下的频率范围内,依据这种方法计算出来的声电转换 波波形与依据完整Pride理论计算的波形一致. 相似文献
80.
岩石波速温度和压力系数的测量方法及其应用 总被引:1,自引:3,他引:1
概述了高温高压实验技术在研究地球深部物质组成和结构等方面所起的作用,认为它是把地球物理模型同地球深部物质组成结合起来必不可少的一个中间环节,通过分析典型的试验结果,介绍了在实验室测定岩石波速温度系数(ρ↓V/ρ↓T)P、压力系数(ρ↓T/ρ↓P)T和岩石本征波速(VO)的方法,以及运用它们进行波速外推的原理,结合前人工作实例,阐明了将此技术与地质及地球物理研究结合,为地球物理测深资料的解释提供实验约束的研究思路,针对在前人工作中实验参数及实验结果存在差异的现象,着重探讨了实验条件和流程对实验结果的影响,认为,在用回归方法计算(ρ↓V/ρ↓P)T时,通常应在大于300MPa的压力段上采集实验数据,以消除岩石内部先存微裂隙的影响;在计算(ρ↓V/ρ↓P)T时,为抑制热裂隙的产生,还应满足不小于1MPa/℃的压力增量;另外,测定(ρ↓V/ρ↓T)P时,实验温度不宜太高,以避免引起岩石内部的矿物相变和物态变化。 相似文献