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1.
G. S. Xeidakis 《Engineering Geology》1996,44(1-4):107-120
Stabilization of the swelling clay structure is attempted by intercalation of Mg(OH)2 and the development of a brucite interlayer between the clay layers. The properties of the product obtained by applying the technique, formulated as described in a previous work, are considered here. The materials used were Wyoming bentonite (USA), Fuller's Earth (UK), kaolinite, illite, lignite, and silica gels. The Mg(OH)2-clay products were examined by the methylene blue dye test, X-ray diffraction analysis (XRD), differential thermal analysis (DTA), and derivative thermogravimetry analysis (DTGA). From the results obtained it is concluded that: the Mg-hydroxide is adsorbed by swelling clays both on their external and internal surface, whereas it is adsorbed on the external surface by non-swelling clays. The internally adsorbed phase of Mg-hydroxide forms an ill-defined interlayer of brucite, retarding swelling, whereas the external phase covers the particles modifying drastically their surface properties, like the adsorption of the MB dye. The material produced after precipitation of Mg-hydroxide on swelling clays (smectites) did not re-expand on wetting or after glycolation. The adsorption of MB dye was also reduced by some 80–90%, due to coating effect, preventing the measurements of the external surface area of the clay by polar molecules. The principal forces involved in the process are believed to be physical adsorption on the external surface, along with chemisorption and some chemical bonding, mostly in the internal surface. Cementation due to crystallization and, in the long term, some pozzolanic reactions take also place. Internal adsorption of the Mg-hydroxide is postulated to be in the form of positively charged mono- and/or small polymers and it is, chiefly, diffusion controlled. Since Mg-hydroxide is internally adsorbed by swelling clays, whereas Ca-hydroxide(lime) is not, and the (Mg, Ca)-clay aggregates are more stable than the Ca-clay or the Mg-one, the combination of the two hydroxides could give better results in soil stabilization than each hydroxide alone. 相似文献
2.
3.
D. Gournis A. E. Mantaka-Marketou M. A. Karakassides D. Petridis 《Physics and Chemistry of Minerals》2000,27(7):514-521
The interaction of γ-rays with smectite clays induces noticeable changes in the structure and physicochemical properties of the minerals. For sodium-montmorillonite, Mössbauer spectra show that γ-irradiation causes a partial reduction of trivalent iron to the divalent state due to hydrogen radicals production from the radiolysis of interlayer water. The XRD results show no change in the interlayer space upon irradiation and therefore the radiolysis of interlayer water causes no measurable changes in the architectural organization of the interlayer environment. Intercalation of simple organic molecules (ethylene glycol, tert-butanol and tetraalkylammonium salts) causes partial oxidation of structural divalent iron and affects the Mössbauer parameters of the M1 and M2 ferric components. Irradiation of ethylene glycol- or tert-butanol-clay composites indicates reduction of trivalent iron to the divalent state. XRD data show that the irradiation of clay-ethylene glycol complex causes collapse of the initial double layer of glycol molecules to a single layer complex. Finally, XRD results show that the effects of γ-irradiation on clay-tetraalkylammonium complexes depend upon the chain length of the organic cations. 相似文献
4.
Sudhakar M. Rao T. Thyagaraj P. Raghuveer Rao 《Geotechnical and Geological Engineering》2013,31(4):1399-1404
Compacted expansive clays swell due to crystalline swelling and osmotic/double layer swelling mechanisms. Crystalline swelling is driven by adsorption of water molecules at clay particle surfaces that occurs at inter-layer separations of 10–22 Å. Diffuse double layer swelling occurs at inter-layer separations >22 Å. The tendency of compacted clay to develop osmotic or double layer swelling reduces with increase in solute concentration in bulk solution. This study examines the consequence of increase in solute concentration in bulk solution on the relative magnitudes of the two swelling modes. The objective is achieved by inundating compacted expansive clay specimens with distilled water and sodium chloride solutions in free-swell oedometer tests and comparing the experimental swell with predictions from Van’t Hoff equation. The results of the study indicate that swell potential of compacted expansive clay specimens wetted with relatively saline (0.4, 1 and 4 M sodium chloride) solutions are satisfied by crystalline swelling alone. Comparatively, compacted clay specimens inundated with less saline solutions (0.005–0.1 M sodium chloride) require both crystalline and osmotic swelling to satiate the swell potential. 相似文献
5.
G. S. Xeidakis 《Engineering Geology》1996,44(1-4):93-106
The damage caused to structures and other human endeavours, on or in the ground, by swelling clay soils is considered as a natural hazard. In order to mitigate this hazard an attempt was made to stabilize the swelling clay mineral structure by the addition of Mg(OH)2. This will turn the swelling minerals, like montmorillonite, into non-swelling ones, e.g., chloride. Accordingly, the various factors affecting the precipitation-adsorption of the Mg-hydroxide by clays, was investigated, and the conditions giving the best results were established. The factors examined were: the base used as precipitant (NH4OH and NaOH); the preparation of the precipitate, inside or outside the clay suspension; the sequence and the duration of the reagents addition; the OH/Mg ratio; the time of clay-chemical contact; and the drying time and temperature. The method, was applied to different clay minerals (swelling and non-swelling). The material produced after the Mg-hydroxide precipitation was examined by the methylene blue dye adsorption test, XRD, DTA and DTGA methods; the results were treated statistically by factorial analysis. From the results obtained, it is concluded that the factors affecting the Mg-hydroxide adsorption by clays are: the base used as a precipitant, the preparation of the hydroxide directly inside or outside the clay suspension, the drying temperature, and the rate of titration of the reagents. Therefore, the best conditions for the laboratory preparation of hydroxy-Mg-interlayers are a dilute (1–2%) and well-dispersed clay suspension, pH between 10–12; some 12 meq Mg2+, as Mg-salt (e.g., MgCl2) per gram of clay, added before the base and followed by the dropwise titration of 1–2 N NaOH solution into the clay suspension, to give a molar ratio OH/Mg of about 1.5; vigorous agitation of the suspension during titration of the reagents; centrifugation and decantation of the supernatant liquid, and drying the product at about 250°C. Satisfactory results are also obtained with the fast titration of the base and drying at 105°C to complete dryness. 相似文献
6.
Thermomechanical model of hydration swelling in smectitic clays: I two-scale mixture-theory approach
Mrcio A. Murad 《国际地质力学数值与分析法杂志》1999,23(7):673-696
A thermomechanical theory of hydration swelling in smectitic clays is proposed. The clay is treated as a three-scale swelling system wherein macroscopic governing equations are derived by upscaling the microstructure. At the microscale the model has two phases, the disjoint clay platelets and adsorbed water (water between the platelets). At the intermediate (meso) scale (the homogenized microscale) the model consists of clay particles (adsorbed water plus clay platelets) and bulk water. At the macroscale the medium is treated as an homogenized swelling mixture of clay particles and bulk-phase water with thermodynamic properties defined everywhere within the macroscopic body. In Part I, the mesoscopic model governing the swelling of the clay particles is derived using a mixture-theoretic approach and the Coleman and Noll method of exploitation of the entropy inequality. Application of this procedure leads to two-scale governing equations which generalize the classical thermoelastic consolidation model of non-swelling media, as they exhibit additional physico-chemical and viscous-type terms accounting for hydration stresses between the adsorbed fluid and the clay minerals. In Part II the two-scale model is applied to a bentonitic clay used for engineered barrier of nuclear waste repository. The clay buffer is assumed to have monomodal character with most of the water essentially adsorbed. Further, partial results toward a three-scale thermomechanical macroscopic model including the bulk phase next to the swelling particles are derived by homogenizing the two-scale model with the bulk water. A notable consequence of this three-scale approach is that it provides a rational basis for the appearance of a generalized inter-phase mass transfer between adsorbed and bulk water. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
7.
A detailed fluid inclusion study has been carried out on the hydrocarbon-bearing fluids found in the peralkaline complex, Lovozero. Petrographic, microthermometric, laser Raman and bulk gas data are presented and discussed in context with previously published data from Lovozero and similar hydrocarbon-bearing alkaline complexes in order to further understand the processes which have generated these hydrocarbons. CH4-dominated inclusions have been identified in all Lovozero samples. They occur predominantly as secondary inclusions trapped along cleavage planes and healed fractures together with rare H2O-dominant inclusions. They are consistently observed in close association with either arfvedsonite crystals, partially replaced by aegirine, aegirine crystals or areas of zeolitization. The majority of inclusions consist of a low-density fluid with CH4 homogenisation temperatures between −25 and −120 °C. Those in near-surface hand specimens contain CH4+H2 (up to 40 mol%)±higher hydrocarbons. However, inclusions in borehole samples contain CH4+higher hydrocarbons±H2 indicating that, at depth, higher hydrocarbons are more likely to form. Estimated entrapment temperatures and pressures for these inclusions are 350 °C and 0.2–0.7 kbar. A population of high-density, liquid, CH4-dominant inclusions have also been recorded, mainly in the borehole samples, homogenising between −78 and −99 °C. These consist of pure CH4, trapped between 1.2 and 2.1 kbar and may represent an early CH4-bearing fluid overprinted by the low-density population. The microthermometric and laser Raman data are in agreement with bulk gas data, which have recorded significant concentrations of H2 and higher hydrocarbons up to C6H12 in these samples. These data, combined with published isotopic data for the gases CH4, C2H6, H2, He and Ar indicate that these hydrocarbons have an abiogenic, crustal origin and were generated during postmagmatic, low temperature, alteration reactions of the mineral assemblage. This would suggest that these data favour a model for formation of hydrocarbons through Fischer–Tropsch type reactions involving an early CO2-rich fluid and H2 derived from alteration reactions. This is in contrast to the late-magmatic model suggested for the formation of hydrocarbons in the similar peralkaline intrusion, Ilímaussaq, at temperatures between 400 and 500 °C. 相似文献
8.
粘土矿物对有机质的吸附是自然界重要的过程之一。科学界对于有机质与粘土矿物的相互作用过程和机制研究仍处
于一个比较薄弱的阶段。该文采用天然有机质赖氨酸（左旋） 和壳聚糖与蒙脱石进行室内合成模拟实验,通过X射线衍
射、化学分析和红外光谱分析的手段对反应产物进行系统研究。结果表明,蒙脱石对赖氨酸和壳聚糖的吸附均存在两种机
制：阳离子交换和有机分子间的相互吸引。赖氨酸在蒙脱石层间的排布有三种构型,随着赖氨酸浓度的增加分别以倾斜
式、垂直呈“之”字形排列,最后形成第二排并可能生成简单肽;氨基酸的净电荷是影响吸附过程的重要因素,主要与pH
值相关。壳聚糖能在蒙脱石层间形成分层结构,溶液的pH值和无机盐的存在都会影响吸附过程。壳聚糖-蒙脱石复合体在
常温常压下水溶液中能稳定存在,而相同条件下赖氨酸易从蒙脱石层间释放,这主要是由有机质本身的性质以及有机质和
蒙脱石的结合方式决定的。 相似文献
9.
苏皖沉积型凹凸棒石粘土矿床沉积环境探讨 总被引：3，自引：0，他引：3
本文对苏皖沉积型凹凸棒石粘土矿床形成时的沉积环境特征、水介质的ｐＨ值、氧化还原条件、温度及盐度进行了讨论。研究表明凹凸棒石粘土矿床形成于碱性、还原、低盐度的浅水湖相环境。与火山作用有关的热水溶液参与了成矿作用。 相似文献
10.
陕西宝鸡市新近系硬粘土包括风成三趾马红土和“古三门湖河湖相堆积”的硬粘土,是西北地区典型的硬粘土地层之一,也是控制宝鸡市北坡黄土塬边大型滑坡分布的关键地层。为了深入认识该类特殊岩土,尤其是膨胀性粘土矿物（蒙脱石和其混层矿物）,根据该类地层的空间分布特征采集了30多个岩土样品,在宏观与细观结构特征分析基础上,利用移液管法、精细X-射线衍射（XRD）技术、乙二醇与乙醚极性有机分子吸附法,完成了样品粒度成分的定量分析和粘土矿物的精细测定,分析其膨胀势,并结合区域滑坡分布与工程边坡病害,揭示其边坡灾害效应。 相似文献
11.
为了研究页岩对气体的吸附机理,在50℃、60℃、80℃ 3个温度点对贵州凤参1井和天马1井的页岩样品进行等温吸附实验,并绘制出了CH4和CO2等温吸附曲线图,计算得到页岩表面自由能,从自由能角度分析页岩对CH4和CO2气体的吸附特性。研究结果表明:当温度一定时,随着压力的增加,页岩对2种气体的表面自由能变化值均呈现出不断增加的趋势,当压力一定时,随着温度的增加,表面自由能会逐渐减小,这与等温吸附曲线上气体吸附量随压力的变化是一致的;页岩对CO2的表面自由能变化值均要大于CH4,表明页岩对CO2的吸附能力比CH 4 更强,可以通过向页岩层中注入CO2来提高采收率;对于吸附能力较强的页岩气藏,可以通过注入表面活性剂的方法,增强活性剂与页岩表面的结合能力,降低CH4占有面积及其与页岩的表面自由能,以此达到促使CH4解吸的目的。 相似文献
12.
A microstructure model of dual-porosity type is proposed to describe contaminant transport in fully-saturated swelling clays.
The swelling medium is characterized by three separate-length scales (nano, micro, and macro) and two levels of porosity (nano-
and micropores). At the nanoscale, the medium is composed of charged clay particles saturated by a binary monovalent aqueous
electrolyte solution. At the intermediate (micro) scale, the two-phase homogenized system is represented by swollen clay clusters
(or aggregates) with the nanoscale electrohydrodynamics, local charge distribution, and disjoining pressure effects incorporated
in the averaged constitutive laws of the electro-chemo-mechanical coefficients and the swelling pressure, which appear in
Onsager’s reciprocity relations and in a modified form of Terzaghi’s effective principle, respectively. The microscopic coupling
between aggregates and a bulk solution lying in the micropores is ruled by a slip boundary condition on the tangential velocity
of the fluid, which captures the effects of the thin electrical double layers surrounding each clay cluster. At the macroscale,
the system of clay clusters is homogenized with the bulk fluid. The resultant macroscopic picture is governed by a dual-porosity
model wherein macroscopic flow and ion transport take place in the bulk solution and the clay clusters act as sources/sinks
of mass of water and solutes to the bulk fluid. The homogenization procedure yields a three-scale model of the swelling medium
by providing new nano and micro closure problems, which are solved numerically to construct constitutive laws for the effective
electro-chemo-hydro-mechanical coefficients. Considering local instantaneous equilibrium between the clay aggregates and micropores,
a quasisteady version of the dual-porosity model is proposed. When combined with the three-scale portrait of the swelling
medium, the quasisteady model allows us to build-up numerically the constitutive law of the equilibrium adsorption isotherm,
which governs the instantaneous immobilization of the solutes in the clay clusters. Moreover, the constitutive behavior of
the retardation coefficient is also constructed by exploring its representation in terms of the local profile of the electrical
double layer potential of the electrolyte solution, which satisfies the Poisson–Boltzmann problem at the nanoscale. 相似文献
13.
To explore the effects of layer-charge distribution on the thermodynamic and microscopic properties of Cs-smectites, classical molecular dynamic simulations are performed to derive the swelling curves, distributions and mobility of interlayer species, and Cs binding structures. Three representative smectites with distinct layer-charge distributions are used as model clay frameworks and interlayer water content is set within a wide range from 0 to 380 mgwater/gclay. All the three smectites swell in a similar way, presenting the characteristic swelling plateaus and similar trends of swelling energetic profiles. The full-monolayer hydrate, corresponding to the global minima of the immersion energy, is the most stable hydrated state of Cs-smectites. The calculated diffusion coefficients of interlayer species disclose the confining effects in all smectites: both water molecules and ions diffuse slower than corresponding bulk cases and they are much more mobile in the direction parallel to the clay surfaces than perpendicular to them. The formed inner-sphere complex structures are very similar in different smectites: ions bind on the H-sites or T-sites and water molecules form cage-like caps covering the ions. Layer-charge distribution is found to have significant influences on the mobility of interlayer species and preference of ion binding sites. A general sequence is proposed to elucidate the preferences of various hexagonal sites (H-sites) and triangular sites (T-sites), that is, tetrahedrally substituted H-sites > nonsubstituted H-sites > tetrahedrally substituted T-sites > nonsubstituted T-sites, but the influence of octahedral substitutions on the preference of the neighboring sites is not obvious. Analysis of mobility indicates that H-sites are more stable Cs-fixation positions than T-sites and smectite with higher fraction of octahedral charges seems to be the most effective barrier material no matter how water content varies although all smectites can immobilize Cs ions in relatively dry conditions. These findings will not only facilitate basic research in geochemistry and material sciences, but also promote the barrier material designing. 相似文献
14.
《矿物学报》2013,(Z1)
In the past four decades, there is a growing use of surfactant modified clay complexes in wide range of applications. The mostly used surfactants to modify the swelling clay minerals are cationic surfactants, such as quaternary ammonium, which consists of two distinct moieties, a hydrophilic head, where the positive charge is concentrated, and a hydrophobic hydrocarbon chain tail. During the surface modification, this kind of surfactant molecules attach on the inner and outer surface of clay minerals, the hydrophilic surface of raw clay minerals may changed into hydrophobic surface. The changes of organophilicity and hydrophobicity of clay minerals enable them used in more wide fields, such as adsorbents for organic contaminant, geotechnical barriers, filling of nanocomposite, etc. 相似文献
15.
揭示页岩气的吸附机理是阐明页岩气的吸附规律及转化条件、建立具有普适意义的定量评价模型的基础.采用GCMC（Grand Canonical Monte Carlo）分子模拟方法,对不同温压条件下CH4和CO2在不同孔径的伊利石狭缝形孔隙中的吸附行为进行模拟,结果表明,分子模拟与实验所得的吸附量归一化到单位表面积才具有相同的内涵和比较的意义.在此基础上进行的对比表明,分子模拟与实验结果相近,奠定了由分子模拟考察页岩气吸附行为和机理的基础:气体吸附于矿物表面的内因（机理）是气-固分子之间的范德华力和库仑力,伊利石表面对CO2的吸附能力比其对CH4的吸附能力强是其结合能更高的反映;CH4和CO2在伊利石表面的吸附虽然并非严格的单分子层吸附,但以一个强吸附层为主;孔径减小到微孔后吸附相密度将发生叠加,形成微孔填充,也是其结合能叠加的结果. 相似文献
16.
Muawia A. Dafalla 《Geotechnical and Geological Engineering》2012,30(6):1311-1321
The swelling of clay when it is subjected to moisture increase is a complicated process found to be influenced by several factors. The clay??s level of response is highly dependent on its mineralogical composition and structure. Practicing geotechnical engineers use the placement state and general index properties to forecast the swelling behavior of the soils. The purpose of this study was to investigate the influence of placement conditions on various clays and to demonstrate that the swelling of a particular clay type should not be predicted using information and trends obtained for other clays with different origins. Clay from Saudi Arabia was used to investigate the influence of initial moisture content and initial dry density on swelling. The prediction models created by other researchers were compared to the measured values in this study. The swelling behavior of both initially dry and wet prepared bentonite was examined, and the rate at which swelling developed in the bentonite clay was studied. The role of clay content in the volume change of sand?Cbentonite mixtures was also investigated. It was concluded that the prediction of clay-swelling parameters should not be based on the properties of other clays with different origins and mineralogical compositions. The trends published in the literature should be taken as a general guide only, and the influence of moisture content and dry density on swelling should be verified for individual sites. Because clay content significantly influences the overall volume change, it should be carefully assessed in each case. 相似文献
17.
Y. Ichikawa K. Kawamura M. Nakano K. Kitayama T. Seiki N. Theramast 《Engineering Geology》2001,60(1-4):127-138
Bentonite clay is a micro-inhomogeneous material, which consists of clay minerals (mainly montmorillonite), macro-grains (mainly quartz), water, air and others. Properties of the saturated bentonite clay are essentially characterized by the montmorillonite and water (i.e. montmorillonite hydrate). We analyze the molecular behavior of sodium montmorillonite hydrate Na1/3Al2[Si11/3Al1/3]O10(OH)2·nH2O by applying a molecular dynamics (MD) simulation method. And by using the MD results we calculate the swelling property of the montmorillonite hydrate, and compare with an experimental result. Next, by using the same MD procedure we treat a montmorillonite mineral with a large number of external water molecules to check the properties of the water. Here we treat pure- and salt-water. Then we calculate the diffusivity and viscosity of water molecules and Na+ and Cl− ions.
For extending the microscopic characteristics of constituent materials to a macroscopic seepage behavior of the micro-inhomogeneous material we apply a homogenization analysis (HA). That is, starting with the Navier–Stokes equation with distributed viscosity that is calculated by the former MD procedure we determine macroscopic permeability characteristics of bentonite for both cases of pure- and salt-water. Then, by using the permeability property we calculate long-term consolidation behavior of buffering clay, which is planed to be used for high-level radioactive waste (HLRW) management. Here the deformation is treated under the well-defined Cam clay model. 相似文献
18.
二元气驱技术(CO2/N2-ECBM)已成为煤层气增产的重要手段,明确CO2/N2在煤层中的竞争吸附规律以及对煤层物性的影响具有重大意义。利用分子模拟软件Materials Studio建立延川南煤层气实际区块温度、压力条件下的煤分子模型。基于巨正则蒙特卡洛(GCMC)方法研究CO2/N2交替驱替煤层气技术中各注入阶段对CH4吸附的影响,明确CO2、N2对煤层孔渗物性的影响规律。结果表明:在CO2注入阶段,煤层中甲烷迅速解吸;煤中气体吸附总量上升,煤基质膨胀效应增强,导致煤的孔隙体积降低。而转N2注入后,由于N2分压作用使得CH4、CO2吸附量呈现出不同程度的降低;当ωN2/ωCO2≤0.6时煤分子中气体总吸附量迅速降低,而当N2饱和吸附后气体总吸附量保持稳定。煤层孔渗物性随着气体吸附总量呈现出迅速增大后趋于平缓的趋势。此外,ωN2/ωCO2>0.6后N2吸附率迅速降低,这会使得产出气中CH4纯度较低,导致后期提纯成本大大增加。因此,当ωN2/ωCO2=0.6左右时,CH4解吸量为最大值,煤孔隙率较高,最有利于煤层气的开发。 相似文献
19.
T. Hueckel 《国际地质力学数值与分析法杂志》1997,21(1):43-72
Isothermal chemo-elasto-plasticity of clays is discussed, to describe strains induced in clay by permeation of it with a low dielectric constant organic contaminant, in the presence of stress. The strain is crucial in controlling permeability changes in chemically affected clay barriers of landfills and impoundments. The theory encompasses chemical softening or yield surface reduction, coefficient of chemical reversible expansion or contraction due to mass concentration increase, as well as chemical sensitivity of bulk plastic modulus. The experiments on chemistry and stress dependent permeability of Sarnia clay performed by Fernandez and Quigley (1985, 1991) are interpreted using this model. The numerical representations of the chemo-plastic softening function and the chemo-elastic strain function, as well as plastic bulk modulus sensitivity to concentration are evaluated for dioxane and ethanol. Specific requirements for the tests for chemo-plastic behavior of clays are discussed. © 1997 by John Wiley & Sons, Ltd. 相似文献
20.
Shear resistance of fissured Neogene clays 总被引：1，自引：0，他引：1
Two types of fissured Neogene clays (SM and WB) were tested in the laboratory using undisturbed and reconstituted specimens. Although of similar age, the clays differ in their geological history: SM clays were deposited in a marine environment, WB are lacustrine clays with a complex tectonic history.
The index properties of both clays are similar and, accordingly, their strength parameters are mutually close. Test results of the more compact and less wet clay (WB) are affected by the sampling and trimming procedures, especially for 38 mm diameter specimens.
Although the behaviour is similar, the origin of fissures is different. For the SM clays, weathering is the main cause and fissuring reaches a depth of about 20 m. WB clays are dissected by macro- and microfissures originating as the result of tectonic processes and volumetric changes (effect of the coal formation underneath the investigated massif).
Cementation of some samples was found and the transition from clays through cemented clays to claystones (soft rocks) is speculated. 相似文献