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1.
Xiao Yi Li Shuang Niu Shengli Li Yanhua Ke Shizhen Deng Hongwen 《Environmental Earth Sciences》2011,64(4):1059-1070
Dielectric measurements, in the frequency range from 100 Hz to 15 MHz, were carried out using an insulating film method, on
shaly and clean sandstone samples, dry, oil-impregnated, partially or fully saturated with fresh water or solutions of NaCl,
at different concentrations. The results show that two kinds of polarization relating to interface dominate: the inner surface
polarization (ISP) at the pore surface in rocks and the outer surface polarization (OSP) on the outer surface of the rock
sample. Both ISP and OSP are of the Debye type and can be fitted very well using the Cole–Cole equation. The dielectric spectra
of ISP reflect the length scale of pore size or throat size, whereas the relaxation strength depends heavily on the inner
pore surface area. Clay contributes to dispersion in rocks, mainly through increasing the inner surface. When the effect of
water content is minimized, the dielectric properties measured on brine-wetted rock samples show great salinity dependence.
The increase in salinity shifts the relaxation spectra to the high frequency end; it also enhances the relaxation strength.
In the frequency range studied, no dispersion in dry and oil-saturated samples has been observed, which underscores the key
role played by water in dielectric polarization in rocks. 相似文献
2.
Electrical impedance of partially molten gabbro was measured as a function of the frequency of the applied electric field. The impedance of the partially molten gabbro was mainly controlled by the volume and geometry of partial melt, which were observed with an optical microscope study of the quenched sample. The experimental results are interpreted by a theory that formulates the electrical property of rocks containing partial melt, taking ionic diffusion in the melt into account. The theory evaluates the contributions from two types of melt-geometry distributed in the rock matrix, namely:
- 1. (a) nearly isolated melt pockets, and
- 2. (b) connected melt along grain boundaries.
3.
饱和局部非均匀土在动载作用下力学响应的研究一直是动力学领域的难点,如何描述非均匀介质的局部结构,衡量其对宏观孔压产生和消散的影响,目前尚无成熟的理论模型和分析方法。基于有关局部非均质土波动理论的最新研究成果,建立能够描述局部结构对孔压增长和消散过程影响的动力学模型。针对周期荷载作用下的一维饱和岩土层,获得孔隙水压分布的解析解。分别以松弛时间和荷载频率为变量,定量地分析这两个参数对孔隙水压发展的影响趋势,并确定两者对孔压发展的敏感区间,以上述分析为基础,提出对应孔压极值时松弛时间和荷载频率的关系曲线。分析结论对非均匀饱和土动力学的理论研究和工程应用有一定价值。 相似文献
4.
Constitutive models for rocks and soils typically incorporate some form of strain softening. Moreover, many plasticity models for frictional materials use a nonassociated flow rule. Strain softening and nonassociated flow rules can cause loss of well-posedness of the initial-value problem, which can lead to a severe mesh dependence in simulations and poor convergence of the iterative solution procedure. The inclusion of viscosity, which is a common property of materials, seems a natural way to restore well-posedness, but the mathematical properties of a rate-dependent model, and therefore the effectiveness with respect to the removal of mesh dependence, can depend strongly on how the viscous element is incorporated. Herein, we show that rate-dependent models, which are commonly applied to problems in the Earth's lithosphere, such as plate tectonics, are very different from the approach typically adopted for more shallow geotechnical engineering problems. We analyse the properties of these models under dynamic loadings, using dispersion analyses and one-dimensional finite difference analyses, and complement them with two-dimensional simulations of a typical strain localisation problem under quasi-static loading conditions. Finally, we point out that a combined model, which features two viscous elements, may be the best way forward for modelling time-dependent failure processes in the deeper layers of the Earth, since it not only enables modelling of the creep characteristics typical of long-term behaviour but also regularises the initial/boundary-value problem. 相似文献
5.
In this study, the effect of diesel fuel contamination on the electrical properties of unsaturated soils was estimated in
the low frequency ranges. For the soils having 5% water content, the electrical resistivity increased with the diesel fuel
contents while the permittivity decreased at higher diesel contents. However, at 15% water content, the variation of electrical
properties was not significant possibly because most of the electric currents should occur through the pore water. The linear
relationship between the electrical resistivity and the diesel fuel contents in soil was developed at 5% water content, which
implied that the electrical resistivity could be used to quantify the extent of diesel fuel contamination in soil. The results
indicated that the electrical properties including the resistivity and the permittivity could give the reliable estimation
on the diesel contamination with the low water content in soil and the frequency applied below 1 MHz. 相似文献
6.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》2000,25(2):189-194
The electrical conductivity of rock depends essentially on pore space geometry and connectivity of low resistive components. This paper presents a method to combine lattice conduction with models of pore space geometry in order to predict the conductivity of porous rock. Key parameter in this context is a quantity called connectivity which in practice can be determined from porosity and formation factor of natural rock if micro structural properties of the material are known. Simulation investigations have been performed to determine the connectivity of random lattices. An approximate equation has been developed empirically which fits the simulation data at conductivity ratios within in the range of 0.5 to 0.001. From comparison with laboratory data is concluded that the electrical conductivity of saturated porous rock can be described by means of random lattice conduction. 相似文献
7.
Relaxation times in the spaces of several stellar-motion parameters are obtained for a number of open-cluster models. The differences between the relaxation times in these spaces increase with the degree of nonstationarity of the cluster models. In the course of the cluster’s evolution, the relaxation times increase in all the spaces considered. During violent relaxation, the stars occupy all domains accessible to them, first in absolute velocity and then in clustercentric distance. The dependence of the coarse-grained phase-space density of the cluster on small initial perturbations of the phase-space coordinates of its constituent stars tends to decrease at times exceeding the time scales for violent and “collisional” relaxation. 相似文献
8.
Prasanta K. Patro Khasi Raju S. V. S. Sarma 《Journal of the Geological Society of India》2018,92(5):529-532
Magnetotelluric (MT) studies along a few traverses, some cutting across the Western Ghats, during the last few years have provided basic insights into the shallow as well as the deeper electrical structure in the regions near and east of the Western Ghat belt. The MT models broadly show a two layered lithospheric electrical structure with an upper high resistive layer (several thousands of Ωm) and a lower moderately conductive layer (a few tens to a few hundred Ωm). The depth of the interface between the two layers is found to vary from about 120–160 km in the south in the SGT to around 80 km in the north in the northern DVP. Another impressive feature that could be noticed in these electrical models is the presence of well-defined major near vertical crustal conductive feature associated with the region of Western Ghat belt, presumably associated with the tectonic evolution of the Western Ghats. Further, these models also brought out several other well-defined conductors that might be linked to structural features like faults, shear zones, etc., in the region. These conductors pierce through the crustal column and some of these, particularly those oriented in NW-SE direction, i.e., oriented transversely with respect to the ambient compressive stress direction of the Indian shield, assume significance in understanding the seismicity of the region. 相似文献
9.
Nano-scale spatial confinement can alter chemistry at mineral–water interfaces. These nano-scale confinement effects can lead to anomalous fate and transport behavior of aqueous metal species. When a fluid resides in a nanoporous environments (pore size under 100 nm), the observed density, surface tension, and dielectric constant diverge from those measured in the bulk. To evaluate the impact of nano-scale confinement on the adsorption of copper (Cu2+), we performed batch adsorption studies using mesoporous silica. Mesoporous silica with the narrow distribution of pore diameters (SBA-15; 8, 6, and 4 nm pore diameters) was chosen since the silanol functional groups are typical to surface environments. Batch adsorption isotherms were fit with adsorption models (Langmuir, Freundlich, and Dubinin–Radushkevich) and adsorption kinetic data were fit to a pseudo-first-order reaction model. We found that with decreasing pore size, the maximum surface area-normalized uptake of Cu2+ increased. The pseudo-first-order kinetic model demonstrates that the adsorption is faster as the pore size decreases from 8 to 4 nm. We attribute these effects to the deviations in fundamental water properties as pore diameter decreases. In particular, these effects are most notable in SBA-15 with a 4-nm pore where the changes in water properties may be responsible for the enhanced Cu mobility, and therefore, faster Cu adsorption kinetics. 相似文献
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为了探讨中-高煤级深部煤层孔隙结构特征和吸附性,以陕西宜川和山西柿庄地区埋深100~1 800 m的中-高煤级样品为研究对象,对样品进行了煤岩煤质分析以及压汞法、核磁共振、低温液氮和等温吸附等测试,结果表明：(1)随着深度的增加,煤层吸附孔含量增多,渗流孔含量减小,渗透性降低,储层物性变差。(2)比表面积和总孔体积在1 000 m附近出现高值区域,随后才出现如前人所述的随深度逐渐降低的趋势,这与小孔的贡献率一致,可见比表面积和总孔体积并非完全由微孔决定,小孔作用显著。(3)深部煤层吸附性是压力的正效应与温度的负效应共同作用的结果,随着压力的增高,吸附量明显增加,温度每升高1 ℃,吸附量平均减少0.25 cm3/g;兰氏压力并不是简单地随温度递增而递增,而是存在随温度变化的拐点(35 ℃),大于拐点温度时,兰氏压力才呈现增高趋势。 相似文献
12.
大陆下地壳高电导率的起源：矿物中的结构水 总被引：5，自引：1，他引：5
大地电磁学的测定结果显示，大陆下地壳可能具有异常高的电导率(10-4~10-2 S/m)。认识这种异常现象的起源，对于更好地理解地球内部的结构和一些典型的地质学过程具有重要的意义。虽然目前有多种机制试图对大陆下地壳高电导率现象进行解释，但是争论依然激烈，已有的模型(含水矿物模型、孔隙流体模型、颗粒边界石墨膜模型和正空穴电子对模型等)都不能提供令人信服的答案。对安徽女山下地壳麻粒岩包体中的主要组成矿物(斜长石、斜方辉石、单斜辉石)的Micro FTIR分析表明：这三种矿物普遍含有结构水，含量分别可以高至~1 700×10-6、~1 600×10-6和~2 400×10-6。麻粒岩中结构水的存在可能会对大陆下地壳的电导率分布产生重要的影响，从而可能为认识其起源提供一个新的解释方法。 相似文献
13.
One‐dimensional analytical solution for mesoscopic flow induced damping in a double‐porosity dual‐permeability material 
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下载免费PDF全文 Heterogeneities, such as fractures and cracks, are ubiquitous in porous rocks. Mesoscopic heterogeneities, that is, heterogeneities on length scales much larger than typical pore size but much smaller than the wavelength, are increasingly believed to be responsible for significant wave energy loss in the seismic frequency band. When a compressional wave stresses a material containing mesoscopic heterogeneities, the more compliant parts of the material (e.g., fractures and cracks) respond with a greater fluid pressure than the stiffer portions (e.g., matrix pores). The induced fluid flow, resulting from the pressure gradients developed on such scale, is called mesoscopic flow. In the present study, the double‐porosity dual‐permeability model is adopted to incorporate mesoscopic heterogeneities into rock models to account for the attenuation of wave energy. Based on the model, the damping effect due to mesoscopic flow in a one‐dimensional porous structure is investigated. Analytical solutions for several boundary‐value problems are obtained in the frequency domain. The dynamic responses of infinite and finite porous layer are examined. Numerical calculations show that the damping effect of mesoscopic flow is significant on the pore pressure response and the resulting effective stress. For the displacement, the effect is seen only at the very low frequency range or near the resonance frequencies. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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A numerical experiment has been applied to explore the potentialities and the limitations of the inversion of IP-affected TEM responses of a two-layer earth with a polarizable layer above (Model 1) or below (Model 2) a nonpolarizable layer. The IP effects have been incorporated into the models via a Cole–Cole complex frequency-dependent conductivity. One of us computed synthetic in-loop and coincident-loop transient responses with added Gaussian noise, and the other performed single and joint inversion of the two sets of pseudo-experimental data. Model 1 turns out to be advantageous over Model 2 in TEM applications and gives a good fit of the Cole–Cole parameters (chargeability, IP time constant, and exponent) even in the absence of a priori information. In the case of Model 2, the lack of a priori information causes problems as to recognize which layer is polarizable, and the fit of the Cole–Cole parameters is generally worse. The layer thicknesses and resistivities are rather accurate in both groups of models, irrespective of whether a priori information is available. As the upper layer increases in thickness (H1), the fit of its parameters ever improves in both models while the parameters of the lower layer, on the contrary, contain a greater error. Joint inversion of in-loop and coincident-loop transients improves the fit in most cases.Relative rms error (σrel) does not depend on the upper layer thickness for Model 1 but decreases as H1 increases in the case of Model 2. The error in joint inversion is times that in single inversion, which means that additional criteria other than σrel may be useful to estimate the inversion quality. 相似文献
17.
Shi Yan Wu Qi You Zhou Gang Wang Lei Yang Cheng Peng Ling 《Environmental Earth Sciences》2011,62(5):999-1011
Based on batch experiments conducted on soil samples in the laboratory, the relationship between dielectric constant and water
content based on electrical capacitance measurement was investigated. Factors that may affect the relationship, such as measurement
frequency, electrode array methods, and soil particle sizes, were analyzed. A model fitting the relationship between dielectric
constant and water content was proposed. The results clearly indicate that even with the use of rod-like sensors, the measured
electrical capacitance with 1 kHz frequency can be used to construct a good relationship between dielectric constant and water
content. Although the electrode array methods (parallel or non-parallel electrode pair) and soil particle sizes do affect
the obtained absolute values of dielectric constant to some extent, the relationship between dielectric constant and water
content remains unchanged. A clear characteristic is the increase reduction in the dielectric constant at near saturation
condition, and the low increase speed when water content is small. The proposed modified VG model incorporated this characteristic
into it and fitted the data better than the reported models. These results suggest that the electrical capacitance-based dielectric
constant measurement can be extensively used and would be useful, especially in the situations where parallel sensor requirement
is difficult to satisfy. 相似文献
18.
N.O. Kozhevnikov 《Russian Geology and Geophysics》2012,53(4):406-415
Effects of induced polarization (IP) often appear in TEM data collected in Yakutia and elsewhere in permafrost areas. Inversion of transient responses using the Cole–Cole model of frequency-dependent conductivity shows fast decaying induced polarization in the shallow subsurface (within 100 m). Frozen ground within these depths has the chargeability (m) in the range from 0.2 to 0.85 (mostly 0.2–0.5); the relaxation time constant (τ) varies from 35 to 250 μs being 50–100 μs on average, and the exponent c is little variable, unlike m and τ (from 0.8 to 1).The latter fact (c ≈ 1) is indicative of a narrow range of relaxation times fitting the Debye relaxation model. Conversion of the complex conductivity into relative low-frequency dielectric permittivity results in values of the order of tens of thousands or a few hundred thousand. These exceptionally high permittivities have no other plausible explanations than electrochemical polarization of unfrozen water that remains bound on the surface of mineral grains at subzero temperatures. The effects of electrochemical polarization are described and interpreted in terms of frequency-dependent surface conductivity, which is controlled by surface-to-volume ratio. 相似文献
19.
LI Bo WANG Xingzhi LIU Hongqi WANG Yongjun TIAN Jie HUO Fei GAO Zhaolong 《《地质学报》英文版》2020,94(2):305-321
Cast thin section observation, scanning electron microscopy(SEM), high-pressure mercury injection(HPMI), and nuclear magnetic resonance(NMR) were used to examine the microstructure of tight carbonate reservoirs in the Lower Jurassic Da’anzhai Member, the central Sichuan Basin. The pore space in the Da’anzhai Member is classified into 2 types and 17 subtypes, with nano-scale pore throats of ‘O’, ‘S’, ‘Z’, and ‘I’ shapes. Poorly sorted pore throats vary greatly in diameter;thus, it is difficult for fluid flow to pass through these pore throats. There are three classes of pore throats in carbonate reservoirs, i.e. isolated pores, pores coexisting with fractures, and large pores and fractures. Isolated pores may provide some pore space, but the permeability is low. Pores and fractures coexisting in the reservoir may have a great impact on porosity and permeability;they are the major pore space in the reservoir. Large pores and fractures have a great impact on reservoir properties, but they only account for a limited proportion of total pore space. The microstructure of Da’anzhai reservoirs, which dominates fluid mobility, is dependent on sedimentary environment, diagenesis, and tectonic process. Pore structure is related to sedimentary environment. The occurrence of microfractures, which may improve reservoir properties, is dependent on tectonic process. Diageneses are of utmost importance to pore evolution, cementation and growth of minerals have played an important role in destroying reservoir microstructure. 相似文献
20.
J.A. Purton N.L. Allan J.D. Blundy E.A. Wasserman 《Geochimica et cosmochimica acta》1996,60(24):4977-4987
We present a new approach for the rationalisation of trace element partitioning between silicate melts and minerals, which is not based on the empirical, parameterised continuum models in common use. We calculate the energetics of ion substitution using atomistic simulation techniques, which include an explicit evaluation of the relaxation energy (strain energy) contribution to this process. Solution energies are estimated for isovalent impurities in CaO, diopside, orthoenstatite, and forsterite. These show a parabolic dependence on ionic radius, similar to the variation of mineral-melt partition coefficients with ionic radius. The success of the empirical models, which often include only the strain energy, appear to have been due to the partial cancellation of energy terms, and to the empirical fitting of the parameters included in these models. Our approach can be readily extended to aliovalent substitution. 相似文献