压汞侵入压实黏土的X射线显微断层成像：对大孔隙几何形态的洞察
X-Ray microtomography of mercury intruded compacted clay: An insight into the geometry of macropores
AI总结：
本文利用X-μCT研究压汞测试后截留在压实黏土中的汞，揭示大孔隙几何形态及墨水瓶效应，并比较了不同含水率和密度条件下MIP与X-μCT所得主导入口孔径的差异。
摘要：
土壤性质（如湿化塌陷行为和渗透性）与土壤微观结构密切相关。迄今为止，包括压汞孔隙度测定法（MIP）在内的多种技术可用于表征土壤微观结构，但所有技术都有其自身的局限性。本研究通过X射线显微断层成像（X-μCT）研究了在MIP测试过程中侵入并被截留在试样孔隙网络中的汞的特征，以深入了解大孔隙的几何形态及可能的墨水瓶几何形态。针对压实马里兰黏土选择了两种含水率和密度条件。对MIP后截留在微观结构中的汞的分布和几何特征进行了表征，并重建了孔径分布。结果表明，对于本文研究的两种条件，大孔隙在试样内均匀分布，其中大多数呈非球形，且纵横比（沿给定线段的最大厚度与最小厚度之比）小于3。由于测试中使用的特定实验方案以及墨水瓶几何效应的影响，MIP和X-μCT得到的大孔隙主导入口孔径不同。由于在降压过程及随后的X-μCT样品制备过程中汞被挤出，X-μCT中仅成像了具有高纵横比的大孔隙体。但在MIP中整个孔隙空间都是可进入的。对于孔隙比更低的试样，由于纵横比更为显著，主导入口孔径的差异更加明显。
英文摘要：
Soil properties, such as wetting collapse behavior and permeability, are strongly correlated to the soil microstructure. To date, several techniques including mercury intrusion porosimetry (MIP), can be used to characterize the microstructure of soil, but all techniques have their own limitations. In this study, the features of mercury that penetrated and has been entrapped in the pore network of the specimens through MIP testing were investigated by X-Ray microtomography (X-$μ$CT), in order to give an insight into the geometry of macropores and possible ink-bottle geometry. Two conditions of water content and density were selected for the compacted Maryland clay. The distribution and geometry features of mercury entrapped in the microstructure after MIP were characterized and pore size distributions were also reconstructed. The results suggest that, for the two conditions studied in this paper, macropores were evenly distributed within the specimens, and most of them with a non-spherical shape, and with aspect ratio (ratio between the maximum and minimum thickness along a given segment) smaller than three. Different dominant entrance pore size of macropore was obtained from MIP and X-$μ$CT, due to the specific experimental protocol used in tests and the effect of ink-bottle geometry. Only the large pore bodies with high aspect ratio were imaged in X-$μ$CT, due to the extrusion of mercury during the process of depressurization and subsequent sample preparation for X- $μ$CT. But entire pore space was accessible in MIP. The difference in dominant entrance pore size was more significant for specimens with lower void ratio due to a more pronounced aspect ratio.
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