龙游石窟砂岩的泥质胶结物研究

本文通过对浙江龙游石窟砂岩的岩矿鉴定,砂岩泥质胶结物质的X-衍射定性及定量分析、扫描电镜观察、差热分析,以了解砂岩的泥质胶结特征,为石窟风化研究和保护加固研究提供科学依据。     

Active Soils of the Niger Delta in Road Pavement Design and Construction

Active soils existing to irreplaceable extents (both laterally and vertically) within the freshwater zone of the Niger delta are known and have been shown to be highly undesirable in their natural forms for road construction. This is because they swell extensively in the rainy season and shrink proportionately in the dry months together with any structure including road pavement constructed with or placed on them. In this paper, four samples of these soils collected from across the Niger delta were subjected to chemical stabilization with slaked-lime and calcium chloride (CaCl₂) to reduce swelling potential while resulting mixtures (corresponding to tolerable swelling limits) were stabilized with Portland cement to improve strength. First, swell indicator (i.e. 24-h free swell index) was found to diminish with increasing stabilizer content while for combined plot (independent of location/percentage fines), about 10.7% and 6% slaked-lime and CaCl₂ were found to be required to achieve the minimum (2.5% free swell) tolerable, normal or non-swell soil condition. Under this condition and for individual soil materials, addition of cement was found to enhance continual increase in MDD, soaked-CBR and durability index such that the soil becomes better compactible, stronger and more durable with increasing cement content. About 2.6% and 14.6% cement contents were found needed to respectively produce sub-base and base-course materials in roadworks with the latter much more durable than the former. The graphs so obtain could also constitute a complete graphical model for preparing deltaic active soils for use as road pavement materials.     

GIS-based analysis of foundation repairs and soil conditions in the Dallas-Fort Worth region,Texas

The Dallas-Fort Worth region is subject to a severe expansive soils hazard, resulting in costly damage to many thousands of residential foundations each year. A GIS is used to examine relationships between a sample of approximately 10,000 foundation repair addresses and geologic and soil conditions. The study results show that foundation repairs are concentrated in areas underlain by bedrock, surficial deposits and soils that promote high shrink–swell potentials. A linear extensibility index, designed as an index of overall shrink–swell potential explains about 48% of the variation in the prevalence of repairs. Repairs are concentrated on soils that underlay many areas of new urban growth in the DFW region, suggesting that the incidence of foundation repairs in these areas will probably increase in the future. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Magnetic properties of oxidized and reduced smectites

 Four smectites with different total Fe contents (two nontronites, one ferruginous smectite, and one montmorillonite) were reduced to obtain a range of Fe(II)/Fe(III) ratios and their magnetic properties measured with a SQUID (superconducting quantum interference device) as a function of applied magnetic field strength at 5 K and as a function of temperature in a field of 0.1 T. The unaltered nontronite and ferruginous smectite specimens showed antiferromagnetic coupling, whereas the coupling in the reduced samples was ferromagnetic; the paramagnetic Curie temperature increased with increasing Fe(II) content. Data collected after cooling samples in both the presence and absence of an external magnetic field of 0.1 T showed that at low temperatures the reduced (ferromagnetic) nontronite and ferruginous smectite samples exhibit a memory effect of previous magnetic field exposure consistent with superparamagnetic or spin glass behavior. The superparamagnetic/ferromagnetic transition temperature, T _f , increased linearly with increasing Fe(II) content for each of the nontronites, but the relationship between T _f and Fe(II) content differed for different clays, thus demonstrating that T _f is sensitive to isomorphous substitutions in the clay structure. The montmorillonite was paramagnetic in both oxidized and reduced forms. Received: 23 March 1999 / Revised, accepted: 27 August 1999     

Removal of Cu2+ and Pb2+ Ions Using CMC Based Thermoresponsive Nanocomposite Hydrogel

In this study, carboxymethylcellulose (CMC) based thermoresponsive nanocomposite hydrogel was synthesized for the removal of Cu²⁺ and Pb²⁺ ions from aqueous solutions. To prepare nanocomposite hydrogel, graft copolymerization of N‐isopropyl acrylamide (NIPAm) and acrylic acid (AA) onto CMC was carried out in Na‐montmorillonite (MMT)/water suspension media and ammonium persulfate (APS) used as initiator. The chemical structures of hydrogels were characterized by Fourier transform infrared (FT‐IR) and X‐ray diffraction spectroscopy (XRD). Lower critical solution temperature (LCST), pH responsivity, swelling, and deswelling properties of the hydrogels were also examined. In addition competitive and non‐competitive removal of Cu²⁺ and Pb²⁺ studies were carried out. According to heavy metal sorption studies results, removal capacities of nanocomposite hydrogel for both metal ions were found to be higher than those of pure hydrogel. The analyzed adsorption data showed that the adsorption process of Cu²⁺ and Pb²⁺ could be explained by pseudo‐second order kinetic model. Moreover, according to competitive sorption studies, it is found to be that both hydrogels are more selective to Cu²⁺ ion rather than Pb²⁺.     

Urbanization pressure increases potential for soils-related hazards,Denton County,Texas

The Dallas-Fort Worth region was the fastest growing metropolitan area in the US in the decade 1990–2000. Rapid urbanization accompanied this population growth. A GIS-based analysis of urban growth in Denton County revealed that 53% of new urban development was on soils rated of low suitability for urban uses by the Soil Conservation Service. This compares to only 15% of urban areas on low-suitability soils prior to 1990. These soils are considered poorly suited for urban uses because they are montmorillonitic expansive soils. Expansive soils are known to cause damage to structures, including slab foundations used extensively in new housing in the Dallas–Fort Worth region. Increased urban development on these soils has increased the potential for soils-related hazards.     

蒙脱石晶体膨胀和收缩机理研究

研究了不同种类和浓度电解质溶液调制的Ca-蒙脱和Na-蒙脱石试样的（001）晶面间距与电解质种类和浓度的关系，进而阐述了蒙脱石品体胀、缩的渗透压作用机理。该机理较以往的理论更好地解释试验观察到的现象。     

蒙脱石热处理产物的微结构变化研究

本文对广东和平蒙脱石及其热处理产物进行了化学分析、差热和热重分析、X射线粉末衍射分析、红外吸收光谱分析、扫描电镜、原子力显微镜及魔角旋转核磁共振等研究。结果表明,蒙脱石在热处理温度为126℃-148℃时,主要脱出吸附水和层间水,这一脱水过程是可逆的。当热处理温度达到659℃时,蒙脱石八面体片中的羟基开始脱失,但层状结构仍然保持,这种羟基的脱失过程对应着八面体片中Al^Ⅵ向Al^Ⅳ的转变。当温度达到900℃时,蒙脱石的层状结构完全被破坏,并有新的矿物相μ-堇青石产生。当温度为1200℃时,则出现方英石及莫来石相。当热处理温度达到1350℃时,方英石及莫来石的含量略有减少,并出现较多的含铁堇青石相。     

Evaluating hydro-mechanical interactions of adjacent clay-based sealing materials

Canada’s Nuclear Waste Management Organization (NWMO) is investigating various geological isolation concepts for Canada’s used reactor fuel (NWMO, 2005). These options are all based on the concept of multiple barriers that include Highly Compacted Bentonite (HCB), Dense Backfill (DBF), Light Backfill (LBF), and Gap Fill (GF). The hydraulic, mechanical, and other characteristics of these clay-based sealing materials have been examined previously, but typically in relative isolation (e.g., Dixon, 1999, Blatz, 2000, Siemens, 2006, Stroes-Gascoyne et al., 2006, Baumgartner et al., 2007). Information on how these clay-based sealing materials interact with each other is needed to understand the evolution and performance of the overall sealing system.A total of twenty-three (23) tests that examine the physical interaction of physically dissimilar clay-based sealing materials were installed and monitored at Atomic Energy of Canada Limited’s (AECL) geotechnical laboratory. This paper describes the process of water uptake, interaction between the components installed, and the role of groundwater salinity on water uptake as interpreted from these tests.     

Iron distribution in the octahedral sheet of dioctahedral smectites. An Fe K-edge X-ray absorption spectroscopy study

The distribution of iron atoms in the octahedral sheet of a series of dioctahedral smectites with varying unit-cell composition and iron content was investigated by Fe K-edge XAS spectroscopy. First-step analysis reveals that the patterns corresponding to backscattering by atoms located between 3 and 4 Å from the absorbing atom are very sensitive to the relative amount of light (Si, Al, Mg) and heavy (Fe) atoms. Detailed modelling of this domain then provides valuable information on the number of iron atoms surrounding octahedral iron. By comparing the number of iron neighbours deduced from EXAFS with that determined from unit-cell composition assuming a statistical distribution, three groups of montmorillonites can be distinguished: (1) clay samples from Wyoming display an ordered distribution of iron atoms; (2) clay samples from Georgia, Milos, China and Washington exhibit a close to random distribution of iron atoms; (3) clay samples from North Africa, Germany, Texas and Arizona display extensive iron clustering. These results complement previously obtained IR results and show that the combination of these two spectroscopic techniques could provide an additional crystal-chemistry-based framework for typological analysis of montmorillonite deposits.