Application of Soft-X ray to Analyze the Micro-Struture of Flow in Porous Media

饱和土壤中液体的流动用著名的达西流线来描述。另一方面，非饱和水流是通过非饱和导电性（KAPPA）来计算的，它是吸力（PSI）或含水量（rheta）的函数。非饱和流动的计算在实际中利用了这个函数。假设土壤由不同粒径的球形颗粒组成，可以从微观角度分析两个颗粒之间的保水体积，得到PSI与rheta之间的理论关系。由于自然界中的大多数砂粒都倾向于具有较高的球形度，因此将其视为球形是合理的。一般来说，土壤中保留的水分为两类。一种是非常薄的薄膜水在一个粒子上，另一种是两个粒子之间的钟摆水。如果我们只考虑直径大于10^<-3> mm的颗粒，则其孔隙中的保水体积可以看作是颗粒上的自由水，而忽略薄膜水。由于表面张力作用于自由水，在不饱和条件下，自由水在两个粒子之间产生一个钟摆环。本文从微观角度提出了一种新的概念模型来分析由不同粒径颗粒组成的非饱和材料的吸力与保水体积之间的关系。此外，所提出的模型已用于估计PSI和rheta之间的关系，假设相同的规则填料。结果总结如下：(1)当相邻颗粒严格接触时，吸力随持水量的增加而急剧减小。(2)对于相同的保水体积，吸力随颗粒半径的增加而增加。(3)在较低含水率条件下，模型计算值与实验结果吻合较好；然而，对于较高的含水量，由于所提出的模型只关注两个颗粒之间孤立的钟摆环，因此无法进行计算。进一步的工作需要分析多粒子间的钟摆环。少

The flow of liquid in saturated soil is described by the well-known Darcy's Low. On the other hand, the unsaturated water flow is calculated by using unsaturated hydraulic conductivity (KAPPA), which is a function of the suction (PSI) or water content (rheta). This calculations of unsaturated flow make use of this function in practice. Assuming that the soil is composed of spherical particles with various grain sizes, it is possible to analyze the water retention volume between two particles from a microscopic standpoint and to obtain the theoretical relationship between PSI and rheta. Because most sand particles in nature are inclined to have high sphericity, it is reasonable to consider them as spherical.Generally, the water retained in soil is grouped into two categories. One is very thin film water on a particle, and the other one is pendular water between two particles. It we focus our consideration on the particles larger than 10^<-3> mm in diameter, the water retention volume in … More the pores can be regarded as free water on a particle, and to ignore the film water. Free water produces a pendular ring between two particles under unsaturated conditions because of the surface tension acting on the free water.In this study, a new conceptual model from a microscopic to analyze the relationship between suction and water retention volume in unsaturated material composed if particles with different sizes is proposed. Furthermore, the proposed model has been used to estimate the relationship between PSI and rheta for the assumed identical regular packing. The results are summarized as followings.(1) If adjacent particles contact strictly with each other, suction radically decreases with an increase of the water retention volume.(2) For the same water retention volume, suction increase with the increment of radius of the particle.(3) Calculated values from the proposed model agree well with the experimental results for the lower water content ; however, for the higher water content, the calculation cannot be carried out because proposed model focuses on only isolated pendular rings between two particles.Further work is needed to analyze pendular rings among multi-particles. Less