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首页> 外文会议>IUYAM Symposium on Theoretical and Numerical Methods in Continuum Mechanics of Porous Materials, Sep 5-10, 1999, Stuttgart, Germany >Macroscopic Swelling of Clays Derived from Homogenization
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Macroscopic Swelling of Clays Derived from Homogenization

机译：均质化粘土的宏观溶胀

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摘要

Swelling clay consists of large flat sheets of deformable silicate structures separated from one-another by an aqueous layer (adsorbed water) . Each clay mineral consists of a 2:1 layer consisting of an octahedral aluminia sheet between two silica tetrahedral sheets. Crystal imperfections and isomorphous substitutions in the smectitic minerals produce negative surface charge density which is neutralized by exchangeable cations to form a diffuse positively ionic atmosphere around the clay mineral surfaces. Swelling phenomena result from change in the crystal dimension when water is incorporated into the lattice structure. When a phyllislicate crystal is put in contact with water, the water penetrates between the superimposed layers and intermolecular forces (hydration and electrical repulsive forces) operate to disjoin the stacked silicate layers. During water uptake, the volume of montmorillonite increases by absorbing water. Water will flow osmotically into regions of higher ionic concentration and particles will separate causing swelling. For low moisture content range (interstices smaller than 50A) swelling is dominated by hydration forces, which consist of bonding forces between the mineral surfaces and the water which arise from the hydrophilic structure of the platelets resulting from the ordering of polar water molecules near the clay minerals (Israelachvili). In contrast, for long-range interactions, swelling is dominated by the electrostatic effect, which is classically governed by the conventional Gouy-Chapman theory of diffuse double layer wherein the equilibrium charge distribution and the electrical field are governed by a Poisson-Boltzman equation. To the authors knowledge a comprehensive microscopic theory capable of generalizing Gouy-Chapman theory to incorporate non-equilibrium effects (such as ion transport and fluid movement) and their correlation with the overall macroscopic response of the clay clusters has not been developed yet. The paper aims to fill this gap. Here we adopt the homogenization procedure to upscale the non-equilibrium version of the Gouy-Chapman theory whose governing equations in the fluid domain incorporate fluid motion and ion transport. This system is coupled with the elasticity problem governing the deformation of the clay platelets in the solid phase. Homogenized equations are derived by a rigorous upscaling of the microstructure. Among other effects, the homogenized results include additional physico-chemical terms, such as disjoining pressure. Unlike experimental results, which have pursued a direct macroscopic view for the constitutive behavior of these quantities (see e.g. Low), the upscaling provides a micromechanical representation for them.
机译：溶胀的粘土由可变形的硅酸盐结构的大平板组成，该大的平板由水层（吸附的水）彼此隔开。每种粘土矿物均由一个2：1层组成，该层由两个二氧化硅四面体片之间的八面体氧化铝片组成。在近晶矿物中的晶体缺陷和同晶取代产生负的表面电荷密度，其被可交换的阳离子中和，从而在粘土矿物表面周围形成弥散的正离子气氛。当水混入晶格结构中时，晶体尺寸的变化会导致溶胀现象。当将叶状晶体与水接触时，水会渗透到叠加层之间，并且分子间力（水合作用和排斥力）会作用以使堆叠的硅酸盐层脱离。在吸水期间，蒙脱石的体积通过吸收水而增加。水将渗透到离子浓度较高的区域，而颗粒将分离而引起膨胀。对于低水分含量范围（空隙小于50A），溶胀主要由水合力决定，水合力由矿物表面和水之间的结合力组成，后者是由粘土附近的极性水分子的有序排列而产生的血小板的亲水结构引起的矿物（以色列）。相反，对于长距离相互作用，溶胀主要由静电效应决定，静电效应经典地由常规的双层双层Gouy-Chapman理论控制，其中平衡电荷分布和电场由Poisson-Boltzman方程控制。据作者所知，尚未开发出能够推广Gouy-Chapman理论以纳入非平衡效应（例如离子迁移和流体运动）及其与粘土团簇整体宏观响应的相关性的全面微观理论。本文旨在填补这一空白。在这里，我们采用均质化程序来扩展Gouy-Chapman理论的非平衡形式，该理论在流体域的控制方程包含了流体运动和离子传输。该系统与控制固相中粘土薄片变形的弹性问题有关。均质化方程是通过对微观结构进行严格的缩放而得出的。除其他影响外，均质化的结果还包括其他物理化学术语，例如分离压力。与对这些数量的本构行为追求直接的宏观观察的实验结果不同（参见例如低），放大比例为它们提供了微观机械表示。

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