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21.
A detailed multiscale analysis is presented of the swelling phenomenon in unsaturated clay-rich materials in the linear regime through homogenization. Herein, the structural complexity of the material is formulated as a three-scale, triple porosity medium within which microstructural information is transmitted across the various scales, leading ultimately to an enriched stress-deformation relation at the macroscopic scale. As a side note, such derived relationship leads to a tensorial stress partitioning that is reminiscent of a Terzaghi-like effective stress measure. Otherwise, a major result that stands out from previous works is the explicit expression of swelling stress and capillary stress in terms of micromechanical interactions at the very fine scale down to the clay platelet level, along with capillary stress emerging due to interactions between fluid phases at the different scales, including surface tension, pore size, and morphology. More importantly, the swelling stress is correlated with the disjoining forces due to electrochemical effects of charged ions on clay minerals and van der Waals forces at the nanoscale. The resulting analytical expressions also elucidate the role of the various physics in the deformational behavior of clayey material. Finally, the capability of the proposed formulation in capturing salient behaviors of unsaturated expansive clays is illustrated through some numerical examples. 相似文献
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High spatial resolution and spectral fidelity are basic standards for evaluating an image fusion algorithm. Numerous fusion methods for remote sensing images have been developed. Some of these methods are based on the intensity–hue–saturation (IHS) transform and the generalized IHS (GIHS), which may cause serious spectral distortion. Spectral distortion in the GIHS is proven to result from changes in saturation during fusion. Therefore, reducing such changes can achieve high spectral fidelity. A GIHS-based spectral preservation fusion method that can theoretically reduce spectral distortion is proposed in this study. The proposed algorithm consists of two steps. The first step is spectral modulation (SM), which uses the Gaussian function to extract spatial details and conduct SM of multispectral (MS) images. This method yields a desirable visual effect without requiring histogram matching between the panchromatic image and the intensity of the MS image. The second step uses the Gaussian convolution function to restore lost edge details during SM. The proposed method is proven effective and shown to provide better results compared with other GIHS-based methods. 相似文献
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In the paper, we present newly developed hydro-mechanical hypoplastic model for partially saturated soils predicting small strain stiffness. Hysteretic void ratio dependent water retention model has been incorporated into the existing hypoplastic model. This required thorough revision of the model structure to allow for the hydro-mechanical coupling dependencies. The model is formulated in terms of degree of saturation, rather than of suction. Subsequently, the small strain stiffness effects were incorporated using the intergranular strain concept modified for unsaturated conditions. New features included degree of saturation-dependent size of the elastic range and an updated evolution equation for the intergranular strain. The model has been evaluated using two comprehensive data sets on completely decomposed tuff from Hong-Kong and Zenos Kaolin from Iran. It has been shown that the modified intergranular strain formulation coupled with the hysteretic water retention model correctly reproduces the effects of both the stress and suction histories on small strain stiffness evolution. The model can correctly predict also different other aspects of partially saturated soil behaviour, starting from the very small strain range up to the asymptotic large-strain response. 相似文献
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天山乌鲁木齐河融雪和河川径流的水文化学过程 总被引:9,自引:3,他引:9
研究结果表明, 含 Ca C O3矿物的溶解作用在乌鲁木齐河源区居主导地位 尽管融雪径流的 “离子脉冲”作用可以释放峰值强度达 3~4 倍的 S O24 和 N O-3 流, 并且引起了总控断面河川径流与之相像的“离子脉冲”现象,但河川径流仍然呈现弱碱性;河源区强烈的含 S矿物的氧化溶解作用,产生大量的 H+ ,被含 Ca C O3矿物的溶解作用所缓冲, 未引起河川径流的酸化乌鲁木齐河以冰川站为界, 以上地区的水文化学过程为矿物的侵蚀- 溶解过程,以下则发生部分矿物的沉淀,如 Ca C O3的沉淀 Ca C O3 的沉淀作用一定程度上又增强了河流的酸缓冲力 相似文献
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Since 1980 when F. Lippmann's seminal paper appeared, ourunderstanding of solubility equilibria involving ionic solidsolutions has been advanced by theoretical considerations as wellas careful experimental studies designed to determine excess Gibbsfunctions. A unified theory of solid-solution aqueous-solutionequilibria as well as the thermodynamic background of thephenomenon of ``stoichiometric saturation' are reviewed.It is shown that Lippmann diagrams effectively summarize thethermodynamic basis of solid-solute aqueous-solution equilibria ofsparingly soluble metal carbonate systems. Clearly, the predictivepower of these diagrams may be limited due to kineticrestrictions. Only when dissolution and precipitation areessentially reversible, favourable conditions to synthesizehomogeneous solid phases can be derived from studies of equilibria. 相似文献
29.
通过一维砂柱实验研究了阴离子表面活性剂十二烷基苯磺酸钠(SDBS)对空气扰动技术(air sparging,AS)修复氯苯污染地下水的强化效果.结果表明,SDBS的加入降低了地下水的表面张力,减小了水气两相毛细压力,从而提高了地下水中的空气饱和度.当曝气量为100 mL/min,地下水的表面张力由72.2 mN/m降至49.5 mN/m时,地下水中空气饱和度由13.2%提高至50.1%,而后随着表面张力的进一步降低,空气饱和度不再提高,反而有小幅下降.通过污染物的去除实验发现,SDBS的加入大大提高了氯苯的去除率,且去除率的变化与空气饱和度的变化趋势基本相符.因此,表面活性剂的加入可以作为空气扰动技术一种十分有效的强化手段. 相似文献
30.
This paper addresses the characterization of the Continental Intercalaire aquifer(CI) in the Tinrhert-East area of Illizi Basin on the Algerian-Libyan border, which belongs to the SASS1 system, one of the biggest transboundary aquifers in the world. This study concerns a superficies of 4 300 km~2. On the basis of Mud Logging borehole data conducted in this part of the aquifer, a realistic characterization of the aquifer was done. The thickness of the CI aquifer varies from 300 m in the south to 700 m in the north, and the depth ranges from 180 m to 320 m. The interpretation of the logs showed that the aquifer is characterized by a maximum net thickness in its southwestern part(more than 600 m), the porosity is very high, ranging from 30% in the west to 24% at the Libyan borders, the permeability is low to medium around 10~(-5) m/s, and the maximum transmissivity values of about 8× 10~(-3) m~2/s were recorded at the center of the study area. The depth of water varies from 235 m to 312 m, and the water flows from south to north, in accordance with the general direction observed in the CI aquifer in the Northern Sahara Aquifer System(SASS). The porosity values obtained from the interpretation of the sonic and density logs permit to estimate the water reserves of this aquifer considered fossil, at thresholds much higher than what was considered until now. 相似文献