Using Synchrotron-Based X-Ray Microcomputed Tomography to Characterize Water Distribution in Compacted Soils
Using Synchrotron-Based X-Ray Microcomputed Tomography to Characterize Water Distribution in Compacted Soils
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DOI：
10.1155/2019/7147283
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发表时间：
2019-05
影响因子：
--
通讯作者：
Zhong-Sen Li;Lian-sheng Tang
中科院分区：
文献类型：
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作者：
Zhong-Sen Li;Lian-sheng Tang
水对非饱和土的水力学行为起着至关重要的作用。非饱和土力学的一个重要问题是确定水在孔隙中的分布及其与土粒的相互作用。本文介绍了基于同步加速器的x射线微计算机断层扫描（μ-CT）在不同土壤中水分空间分布的一些结果。首先在含水量约10%的条件下制备三种材料（玻璃微珠、天然砂和粘土），在500 kPa的垂直总应力下静态压实，然后在18或20 keV的能量下进行同步加速器x射线扫描。对样品的气、液、固三相三维显微结构进行了重建，得到了一些新的观察结果：(1)碘基对比剂（KI）可以将水的峰值灰度值从110提高到122，增强了气-水对比，有利于水相的分割；（ii）利用μ-CT和图像重建技术表征了压实玻璃微珠和砂土中的水分分布。相分割法测得的水分含量分别为10.2%和9.3%，与烘箱干燥法测得的水分含量相当，玻璃珠和砂的水分含量分别为9.7%和9.4%；（iii）当水与烘箱干燥的颗粒混合时，优选分布在骨料中，并且观察到以骨料为主的3D结构。然而，即使分辨率为0.65 μm/pixel，也无法确定所研究材料的水相。
Water plays a vital role on the hydromechanical behavior of unsaturated soils. An important concern in unsaturated soil mechanics is to determine the distribution of water within voids and its interaction with soil grains. This paper presents some results of the spatial distribution of water in different soils using the synchrotron-based X-ray microcomputed tomography (μ-CT). Three materials (glass beads, natural sand, and clay) were first prepared at a water content of about 10%, statically compacted under vertical total stress of 500 kPa, and then scanned by synchrotron X-rays at an energy of 18 or 20 keV. The three-dimensional (3D) microstructure of the samples including air, liquid, and solid phases was reconstructed, and some new observations were obtained: (i) the iodine-based contrast medium (KI) can increase the peak greyscale value of water from 110 to 122, enhance the air-water contrast, and thus facilitate the segmentation of water phase; (ii) in the compacted glass beads and sand, water distribution is characterized using the μ-CT and image reconstruction technique. The water contents obtained by phase segmentation, i.e., 10.2% and 9.3%, are comparable with those measured by the oven-drying method, i.e., 9.7% and 9.4% for the glass beads and sand, respectively; (iii) water is preferably distributed within aggregates when it is mixed with the oven-dried particles, and an aggregate-dominated 3D structure is observed. However, it is impossible to determine the water phase for the studied material even with the resolution of 0.65 μm/pixel.