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

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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